That is the argument I made to quite a few Bernie supporters in 2016. In particular, I mentioned that if nothing else, think of the Supreme Court, which may affect us and our kids for decades to come. I didn't even realize just how shitty the Court might be.
My Bernie-loving friends all said they either voted, writing in "Bernie", or didn't bother. The most childish thing they all said: they wanted the system to break down because both parties were the same and maybe it needed to blow up before being rebuilt. Yeah, how does that work exactly? For one thing, both parties may suck to some degree but their policies are NOT the same, certainly not for environmentalist and social issues. How does letting a wanna be dictator get the reins make the system break down? It doesn't. It just lets the GOP cement power and continue tilting the field in their favor with things like gerrymandering and "voting reform" in certain areas (ie, making it as difficult as possible in those areas to actually vote. You can imagine which areas these might be.)
A vote for an independent is at best a wasted vote and at worst a half vote for the GOP if like my friends you align much more with the Democrats. I personally have no issues whatsoever with voting lesser evil. We all do this throughout our lives every days...we pick a traffic route to avoid really bad traffic, not because we are excited to go a certain way. And not to mention there hasn't been an independent candidate whose platform I liked any more than the Democrats so that makes the decision even easier. Hero worship of politicians is sick; these are civil servants that work for us, not gods to bow down to or cheer like it's some hometown high school football team.
The worst are the fucking Green voters. Let's siphon votes away from the Dems and help the one party absolutely dedicated to wreck the environment, how green is that. Look at all the repeals and reversals Trump did in just four years, especially if something was signed by the brown man just before him.