I have to deal with a lot of variations on this, from people in my undergrad major being so depressed from climate change that they hope everyone dies really fast (especially humans, they feel bad for the animals, but they want the humans to die so bad even more than I do (amazingly) that they are willing to sacrifice some species in hope that eventually it will birth a new Pleistocene....and as a scientist, can I just say, the Pleistocene is VERY attractive and followed a much warmer planet than we have now, and a mass extinction of dinos in the Jurassic/Triassic. I love the Pleistocene very much I would think a lot of vegans do, or animal rights vegetarians, lots of big cute hairy mammals stepping on ugly tiny humans). ...to people like you describe, who just don't care, because they're stupid. I think it helps if you admit that they're low-average IQ or low EQ people. People who don't care either have low EQ (but often young intellectuals) or lowish IQ (still average, but not terribly bright, like some of your cousins or childhood neighbors, just those people who watch the Kardashians....they aren't retarded and can pass driver's ed...but we all have our doubts, sis). THAT HELPS. I don't care what the Internet says or what political correctness says. It helps me to remember a lot of people are less intelligent than me, and other people are more intelligent than me. You are lost, though, when you forget other people "are more intelligent than me." That sets you up for a Dunning-Kruger dumb-fest, but as long as you remember humans were learning things in different races on different continents for thousands of years before you were born, and some are still physicists, you'll be ok! The worst people I've met, tbh, are people who think they are smarter than climatologists with "common sense" or people who have so much "empathy" that they enable these trash humans. I am just like, stop enabling them, if Jesus isn't coming, who cares if we tell them they're wrong?
So I don't think I've given a response to this one, because there's not an easy answer. Intelligent and highly educated people who want all humans to die (and don't care if some species die with them, out of kindness for the species in their view) are pretty much unreachable. These people are smart, they know climate change is happening, they know we have the sixth mass extinction, and they are willing to sacrifice a few other species if humans die oh-plz-god-plz-kill-humans-and-be-wooly-mammoths-and-smilodon-again!!! I get their point of view. I don't agree with them, because all humans aren't equally responsible for climate change, and I do not agree with "sacrificing" other species to human death (no matter how initially appealing). Those people are lost causes though. Maybe you'll catch one and change their mind in an off-moment, but these people are gone, and they're as smart or smarter than you, so stop wasting your time.
The hypocrites, the people who say farm animals aren't cute, or we can't do this because people in food deserts can't be vegan, my really nice vegan friend says to treat these people like children. She says it helps to frame them as children. When you think of them as being childlike, instead of being morons (because likely they have average, even if low-average, intelligence) you might have more empathy for them and be able to get through to them. God bless those vegans. God bless those holy vessels of kindness. I'm not one of them.
I'm here to talk to those with ears to hear, like Jesus. Ironically, he didn't have time for their ******** either.