Tumblr Culture continues to puzzle

I have trouble wrapping my head around the point of "blocking" someone on Tumblr. So far, it's gone like this:

Someone: says something deeply stupid, and insists that anyone who doesn't agree with Deeply Stupid Thing is an evil, hateful apologist for BadThing.

Me: Your position on Thing is not tenable, because Reasons Given. Also, I don't take marching orders from random strangers on the internet--I decide for myself.

Them: [blocks me on Tumblr]

Result: I see a truncated first line of their reply on the message they blocked over the Tumblr activity log, which is incomprehensible because it is truncated. Clicking through to the message, I find their log empty, because I am blocked.

Okay, I now cannot see any more Deeply Stupid stuff they may say. I think I "won", though I'm not sure what the point of it was.