Who is 'we'? Why is Ukraine worth fighting for? Are you willing to put you or your children at war with Russia to 'protect' a country that nearly 100% of Americans can't find on a map? Yeah I thought so. I love all of these patriotic armchair soldiers you find on the internet.
Ukraine is worth fighting for because if the Russians manage to rebuild the Soviet Union as the new Russian Empire, we no longer have the manufacturing base to stop them from taking over Europe, period. If we must fight Russia, better to do it now, while Russia is at best a rusty tiger and we still have something of a military and an industrial base, than fight Russia later when we've lost all our manufacturing base and stood down most of our military. Either way there's a chance the conflict goes nuclear, but if this war happens later we'll be the ones who must make it so. Our alternative is to accept all of Europe as eventually being part of the Russian Empire. That does not stop the war though, it just shifts it to between the Russian Empire and the Chinese Empire.
tl/dr: Only a fool allows an enemy to defeat him in detail.
I'd suggest you study Operation Rolling Thunder. Soviet Union under Gorbachev, refused to back Iraq in the Gulf War, like they did for North Korea or North Vietnam.
http://en.wikipedia.org/wiki/Operation_Rolling_Thunder
Putin wouldn't hesitate having well trained Russian pilots put on the uniforms of Iranians or other adversaries.
I'd suggest you read up on Iranian aerial victories during the Iran-Iraq war; now imagine them being directly backed by Russia.
http://en.wikipedia.org/wiki/Iranian_aerial_victories_during_the_Iran-Iraq_war
Putin might hesitate. For one thing, that is very expensive both in money and in trained personnel. One modern jet equals two pilots equals maybe fifty trained technicians. Putin does not have the combined output of a dozen nations to rape for his war machine. For another, there is a considerably larger differential between the quality of our pilots and the quality of Russian pilots than existed in the seventies. And don't forget, those Iranian pilots were trained in American tactics and flying American jets against Iraqis trained in Soviet tactics and flying Soviet jets. Most of those kills were by F-14 Tomcats, at the time our own front line naval fighter/interceptor and in some ways still better than the Hornets that replaced it. Not only was Iraqi socialism far short of communism, but the inevitable defeat would have been disastrous for Soviet arms sales (then a much more important part of their economy as virtually the only source of foreign currency.) As it was, the effect was significant; had the Soviet Union (then in its death throws) attempted to back Iraq, it would have had virtually no arms sales. The first Gulf war, and even the Iran-Iraq war, took place in a far different world technologically than the Korean War (in which Soviet fighters were at least as good) or the Vietnam War (in which Soviet fighters had advantages which, properly used, made them competitive and sometimes dominant.)
Those that fought for their own freedom while under the yoke of occupation for 5 decades "ended" the cold war.
Not blustering US presidents that barely had a conscious thought beyond selling weapons to our various enemies at the time.
I disagree. With Carter, the Soviets were able to set the terms of strategic weapons agreements to a level they could afford and to levels which granted them an advantage. With Reagan, they could not, for Reagan did not HAVE to have strategic weapons agreements. He would not accept the Soviets having an advantage unless they paid for it, and in building up our military forced the Soviets into social experiments that directly led to the fall of the Soviet Union in an attempt to make a top-down, centrally planned economy as productive as a free market capitalistic economy. The Soviets had absolutely no problem crushing every revolt, but such a repressive society simply cannot be as productive as a free society. Gorbachev tried to maintain the Soviet Union by expanding freedoms, but lifting the boot allows people to get out from under it.