I was raised in a particularly right wing environment, grew up with those values, and have shifted dramatically leftward in my adulthood, and I can say with absolute certainty that you’re either lying or willfully ignorant. Are parts of the online left prone to litmus tests? Yes, but most often in the sense of “hey, I’d appreciate it if people who claim to be in my corner don’t join hands and sing Kumbaya with people who want to eradicate my particular minority from the face of the Earth, please.” They’re a reaction to intolerant right wing fanaticism, rather than a statement of intolerance themselves. You have to go all the way around to the extreme fringe of tankies way out on the left arm of the political-alignment horseshoe to find a level of ideological fervor equivalent to what is now mainstream in right wing politics. The right pioneered single issue voters with the Moral Majority way back in the Eighties, and have led the charge on (sometimes literally) demonizing their opponents since the early days of talk radio. I know, because I was there.

If the modern left doesn’t really want to try and find common ground with a right wing that views them as something between subhuman scum and actual literal hell spawn, I’d argue that’s entirely the right wing’s fault.