Too many people have peed in the pool
I'm not active on twitter, but from what I've seen, particularly in the aftermath of GamerGate, is that it's a putrid mess of hatred, threats, and bigotry. The problem doesn't so much seem to be that people are <i>defending</i> others, but that they are <i>attacking</i> them.<p>I never really saw the point, but it in the past few years it has seemed even more pointless. You just can't have a good, nuanced conversation in 140 characters. You can only shout one-liners and threats. It's what the medium seems designed for.