I think both twitter and tumblr have the ability to be very toxic, but it greatly depends on what type of social circles you keep. Tumblr feels like a more accessible version of Livejournal, where depending upon who you follow/where you go, you can be larg

I actually am finding message boards to be more toxic right now, not all of them, but a bunch are really vicious and fraught with racism, misogyny and homophobia. It makes me feel bad to read them so I mostly quit going.

There are definite exceptions, not trying to paint them all that way.