I try to only join the discussions that interest me, more so than the ones that are, well, stupid. Sometimes I find myself in a long drawn out pointless argument with someone, but usually I only keep the debate going if they make reasonable arguments instead of just focusing on one dumb little thing that they think gives them the upper hand.

This goes for all discussions really. Join in, but try to recognize when you're wasting your breath. I struggle with it sometimes, but ultimately it's still nice to engage with similarly minded people.