Because every day millions of people give away their work.

I give away my work. I've dealt with rude people using software I made since I was pretty much a kid, those people didn't know who their vitriol was directed at.

What makes this guy so special that to spite the vitriolic subset of all users he gets to be the one who throws a wrench in a project?

I said this in a comment below:

You think the kind of person who would insult a library maintainer on Twitter is going to read his Github issue?

"Oh it stopped getting updates" "Good, now my code won't break anymore!" "Security vulnerabilities in libraries? What?"

He's literally only spiting the very people who make projects like this worthwhile, the kinds of people who would want to submit PRs, make useful issues, and people with a genuine interest in the project, exactly what he's saying he lost.