I don't see what's wrong with this, specifically. It's his account, he can block whoever he wants.
People take this stuff way too personally. I've blocked a few people simply because I don't like their stuff in my feed. One of them bugged me for months afterwards to unblock him, even though it's completely inconsequential and I don't say much interesting anyway.
IMO this is a flaw with twitter. Blocks are two-way: I don't see their stuff, and they don't see my stuff. But whenever I'm blocking someone, it's just because I don't want to see their stuff. There's no reason to tie those together.
In any case, how a person manages their own Twitter account is their business. If they use it to say something ridiculous then by all means attack it, but going after them merely for blocking people is ridiculous.