The difference is atheists may be correct, but nowadays whether you're religious isn't, on its own, a huge prediction factor in how you affect others' lives.

When your politics is lib or reactionary, when you're racist, or nationalist, or just deliberately ignorant and loudmouthed about world politics, you are by definition actively and deliberately conspiring to make peoples' lives worse. Those people affected are often minority groups, and/or friends, family and comrades. But whatever kind of human it is, it should be obvious why it's personally important to us to oppose that.

I won't at all deny that society has historically been a lot more hostile to vegans than vice versa. I grew up a vegetarian me whole life and that got enough of that unwarranted abuse as it is. But I'll be honest, in my personal experience, I've met about a hundred vegans who weren't bothered to talk about it (but were frequently harassed by others for their veganism anyway), five vegans scream abuse at me, and between zero and one who wanted to engage in a conversation or saw me as someone to be convinced. I just think it's a different kettle of fish.

I don't consider it dumb, we don't universally dunk on voting, but I think most of us would say it's borderline meaningless. The end result of Biden's time in office vs. Trump's time in office thus far are almost indistinguishable. They both happily support the pursuit to bomb other countries, actively fuel and support overseas wars, attempt coups on foreign governments, blockade Cuba against the wishes of the entire UN, torture innocents in black bag sites, lock up children, imprison people en masse, watch millions suffer without actually reasonably helping, etc. Biden's term in office has overseen a horrific reversal in abortion law and has directly made active efforts to limit the actions of unions, and so forth - that sounds not very distinct from fascism to me.

Main point of the post is "We'll talk about it later" has been the general attitude from liberals to leftists since the beginning of time. We're ALWAYS just averting a crisis right now and it turns out that right now is never the time to actually make constructive change.