I agree. You’d be a better person to just let it go. Or as my mom would say, “Don’t stoop to his level.”
Look at it this way: I’m going to assume that your father, while he may be modestly well known in his field, isn’t really a celebrity. He hasn’t had a biography written about him, right? He hasn’t had lots of newspaper stories written about him that mention his personal life, right? So how is he different from anyone else in his field famous enough to have a Wikipedia page? Do you really think that the other moderately famous people in his field are all wonderful people? Do you really think that none of them have secrets about their personal life that aren’t mentioned on their Wikipedia pages? If their personal lives haven’t been posted to Wikipedia, why should your father’s? Wikipedia isn’t a univeral source of all knowledge. In particular, it doesn’t contain damaging personal information that can’t be attested in biographies or news stories.
If law enforcement people come to you and ask about your father, you’re obliged to tell them what you know. If journalists or biographers come to you and ask personal questions about him, you could tell them what you know about him. On the other hand, if you post facts about your father to Wikipedia that aren’t attested in print, it will probably be deleted. If you post facts about him either to Wikipedia or to your own webpage that could be considered libelous, you better be prepared to prove what you’re claiming in court. If your father is as much of a jerk as you claim, he might try to sue you over your statements.
I’d recommend writing every word you want to post…and then trashing it. Maybe read it out loud to yourself or someone important first.
ISTM the actual writing could be cathartic, and give you what lissener needs, without actually having a negative effect on anyone, as understandable as the desire for revenge is.