I can believe that, but I also have to take those claims with a grain of salt.
Aside from Taleb, I don't recognize any of the people who claim Fridman blocked them, so for all I know, they tweeted obnoxious stuff at him and then complained about being blocked. Taleb is extremely abrasive, so I can't fault anyone for blocking him.
If it was like Yann LeCun and Andrej Karpathy complaining that Lex blocked them, then I'd question how aggressively Fridman blocks people, but if it's random Twitter accounts that seem to just shitpost all day, why do they have a right to communicate with Fridman?
Sure, without making an entire Medium article for you, which I don't have the time to do, I can't prove they weren't all shitposters, although there are some notable names, but that would be a lot of them.
I'll also direct you to the moderator list of the /r/lexfridman sub. No real people, none of them ever comment, and his subreddit is one of the most [deleted] I have ever experienced. If you look at reveddit, also check the comments. Quite telling. https://www.reveddit.com/v/lexfridman/?localSort=num_comment...
If your response is "maybe he just likes a heavily curated subreddit" then all I can say is keep coming back.
For being so open minded, he sure does have an incredibly tight grip on information control. This is coming from someone that used to think Lex was the cream of the crop.