This is an incredibly toxic mindset. Without real proof of what you claim, you're just deciding that people's opinions don't count if they're far enough away from your own. People are becoming nihilistic because that's basically the best case scenario right now. It's obvious that voting for Democrats won't work to fix the big problems we have, and if you try to go around the Dems with a reasonable outsider like Sanders, they will literally just fall on their sword and ensure the nut job gets elected instead, while simultaneously blaming you for not falling in line hard enough for their horrible candidate.
Are the commenters you're referring to shills, or do they do a shitty job arguing their case? Both can't be broadly true.
Are the commenters quitting because they get yelled at, or are they shills who will keep writing that stuff until they stop getting paid? Again, both cannot be broadly true.