Why do liberals always block me on Twitter?

I'd get it if I was spouting memes or slurs or harassing them, but that's never the case.

Just 15 minutes ago I got blocked. I thought we were just two people having a civil discussion, and suddenly "You are blocked from following and viewing Tweets. Learn more."

Why do they do this? With all the talk about the bubble effect in social media etc. you'd think this sort of behaviour wouldn't be so rampant anymore. I see opinions I disagree with all the time, and I've never blocked anyone.