The tone, the mean-spiritness, discussing posters instead of issues. Even if you don't start that way, you become what you try to resist as a matter of survival. But some are quite mean.
However, some people just cannot deal with politics due to disagreement and probably avoid it for that reason.
My Message to President-Elect Donald Trump:
America did NOT became great because of what government did. America became great because of what the U.S. Constitution prevented our government from doing. The people made America great.