DHH is the CTO, not the CEO. And, like you, most of the Twitter mob had no idea what Basecamp was before starting to call him Nazi, white supremacist, racist, etc.
Someone (you?) blocked on Twitter is inconsequential and not relevant.
I used Basecamp's free tier for a personal project and have listened to quite a few podcast interviews with DHH. I used to respect him and the company culture he helped build. I never called him any of those things. Don't be so presumptuous just because I got CTO and CEO mixed up.
Sorry, I didn’t meant to accuse you of calling him something, just to point out blocking aggressive strangers on Twitter is the rational thing to do instead of something reprehensible