It really depends on what happened during that 1 second. The answer could certainly be "yes" depending on how heinous it was. Your rhetorical question bears an unfortunate resemblance to the father of rapist Brock Turner arguing his son shouldn't go to prison for "20 minutes of action".
In Stallman's case, his crime appears to have been white knighting for his dead friend on a mailing list, and during the ongoing discussion, Stallman was his usual Socratic self. He wasn't entirely "cancelled", but there was a huge fallout because he didn't consider his audience properly.
There's nothing wrong with having a debate on the age of consent, it's clearly an arbitrary dividing line that varies between jurisdictions and cultures, there is no right answer other than "at some point near the end of adolescence" but the absolutely worst place you could have that debate is during a discussion of whether a 80-something man had sex with a 16-year old girl being coerced by a child sex trafficker.
Pathos is as important as logos.