No one is ever going to make a winning argument with a direct comparison to Nazi Germany, that's for sure. People are always going to compare the horrific outcome, and never look at the much more subtle underlying causes.
IE: every citizen of Germany at the time was a cigar chomping, mustachio-twirling villain spitting Jew-hatred with every syllable, chanting toss Jews into gas ovens. It couldn't possible be that most were just normal, average, ordinary people who allowed far too much power be given over to two-bit politicians who promised an easy way out for everything that ailed them, with no thought given to what could actually be done with that power.
So of course today, everyone knows they're not cigar-chomping mustachio-twirling anti-semitic villains, so what possible harm could there ever come from allowing far too much power be given over to two-bit politicians who promise an easy way out for all that ails?
So while you'll never win any argument making a direct Nazi comparison conjuring up the outcome, it is possible to make the point that the *same* weakness of human nature Nazis used to come to power can be exploited without the exploiter actually being a Nazi, and for different purposes and outcomes than tossing people into gas ovens.
Nazis were able to exploit an already festering resentment of and hatred for Jews, a great "other" in which all the problems facing Germany could be pawned off on. Humans being human, tend to love a good scapegoat. They took to it gladly.
If you can look to someone else as the source for all your problems, or even if a politician can convince you that the politicians himself isn't a big source of your problems, but some universal "Other" is, then many will take the easier way out. And once the "other" becomes the source of all problems, then people will violently reject *ANY* inference ever that they themselves are part of their own problems, not that it's all other's fault. And guaranteed: the one group that absolutely is forbidden to ever point this out, is the "Other" themselves. Any member of "Other" that dares ever suggest that they aren't the problem, and that people/politicians exploiting them/etc are more likely the source of their own problems, will absolutely be crucified.
Germans happened to target a very specific 'other' in the form of Jews- the example is so specific that most believe it simply can't ever happen again, and so too, the underlying human nature behind it (in fact, WHAT human nature, all cigar-chomping villains, remember?) can't ever surface again either.
But an 'other' so broad like "the rich"- I mean, who are these people anyway? Basically, whoever you want them to be. And OF COURSE the rich are responsible for all that ails. And OF COURSE some politician needs to be given all sorts of power to make things right again. And OF COURSE (and actually this is true) the end result will wind up to be vastly different than anything to do with Nazi Germany. So OF COURSE, one cant make the comparison, or in fact even bring up the whole subject. And OF COURSE, least of all, an 'other'.
Here is the underlying and fundamentally analogy breaking difference though. The Jews were targets and outsiders before the rise of the Nazi party, they were already disenfranchised and vulnerable. The Nazis exploited this to blame them because they were already unpopular and had no way to defend themselves. What's more, they didn't stop there, they also singled out the disabled, communists, gypsies, homosexuals, etc. as being the source of the problems of the German people. It was a broad, anyone who isn't in the image of the ideal physical and mental German needs to be purged.
Here, we have resentment building against the very wealthy for the opposite reason, not that they are outsiders but because they run the system on two ends. First, they are the ones who control industry. They are the ones who decide whether jobs get moved overseas or jobs get replaced by machines or wages get slashed or hours get cut or benefits get removed or prices get raised because the almighty shareholder demands it. You can agree or disagree that there is nothing wrong with trying to maximize your personal wealth within the bounds of the laws, but you cannot deny that when a decision is made for the benefit of shareholders and to the detriment of workers and consumers they are not going to be happy about it, which brings me to the first point it is reactive to things that wealthy have done as opposed to being scapegoated for things they had nothing to do with as the Jews were.
Secondly, they have a virtual stranglehold on the political process right now. With campaigns, in particular presidential campaigns but also governors, senate, and congress in places with a contested electorate, now costing hundreds of millions to billions of dollars and prices only going up, politicians are entirely beholden to special interest which are now dominantly corporate and controlled by the extremely wealthy. Any politicians who would oppose the interests of big business is basically a political nonstarter. Now, there are some who would oppose specific big businesses, like a democratic politician opposing oil to a degree, but that usually just means they are beholden to a different group such as the big tech companies. Through control of the political process, a number of laws have been passed that limit the exposure of the wealthy, legally, and keep them from being held responsible for misconduct by keeping liability with the corporate entity rather than the people behind it, for just one example.
This has gotten to the point where the entire economy is being held hostage by institutions that have been declared too big to fail or too big to prosecute. Without derailing the thread into a discussion of whether the bailout was good or necessary, the fact of the matter is that without it the economic upheaval by multiple large banking institutions collapsing simultaneously would have been catastrophic at all levels. There used to be laws to prevent institutions from getting this large and getting this much control, but those have been eaten away by corporate written legislation that eliminates things like caps on how much of a market you can control.
More than that, the antipathy for the rich tends to be more focused than that. I don't see many leftists calling for the heads of Bill Gates or Warren Buffet, the two richest Americans even when they are talking about sticking it to the 1%. The reason being that some people of wealth believe that with great wealth comes great responsibility, to turn a phrase. Bill Gates and Warren Buffet have given back to the world, spent enormous sums of personal wealth they didn't have to just to make lives better, and for the most part we respect that. You didn't see that kind of consideration from the Nazis with the Jews. More, the anger towards the wealthy is more genuine, that is, something people have come to their own conclusion where the persecution of the Jews was manufactured, a government sponsored propaganda campaign being necessary to build that resentment.
So on the one hand we have a government manufactured outrage against people who have no real mechanism to defend themselves for things they had nothing to do with in a broad fashion while on the other we have growing personal resentment against people who control the system in which they live whose personal actions have had a detrimental impact on their life and livelihood in a specific fashion. This is the difference between hating your boss because they cut your wages and hating your coworker because your wages were cut and he happens to be Jewish. There is no comparison here. If you wanted to be even remotely accurate with a historical analogy you might go towards something like the French Revolution or some other historical uprising against an upper class by the lower classes but the idea that the poor and downtrodden are somehow equivalent to the Nazi party is laughable.