it feels like you're besieged from all sides.

Ehhh... in my experience tumblr really is the easiest social site to avoid trolls and opinions contrary to yours, just as the article says. The only default means of communication, reblogging, makes comments hard to see unless you're already following the commentator - you pretty much have to explicitly look for them.

But at the same time you see all the comments and content from the like-minded people you follow, making tumblr into the perfect echo chamber. Which directly results in the toxic communities your quote is referencing (https://twitter.com/tumblrtxt)