Speaking for myself the first HUGE red flag out of Stallman was his famous comment about pedophilia circa 2006, which this "Stallmansupport site" actually addresses.
https://stallmansupport.org/debunking-false-accusations-agai...
The defense seems to be summed up in this line: "Whatever the reasoning that led Stallman to write those statements, the fact is that later he changed his mind."
It seemed pretty clear what he meant, and walking it back 13 years later under pressure doesn't make me think that he didn't mean it the first time.
None of which changes anything about how much a person should or shouldn't support Richard Stallman.
He was also credibly accused of raping minors multiple times, although those accusers were too afraid (justifiably so) to let us see those accusations play out in court.
Edit To be entirely clear: I am not defending Trump, he should be in prison, not the White House.