I think it really depends on the person - like, if it's Arafat or Hitler, yes, you stand a good chance of being able to vent.
On the other hand, if a person wants to post a "tribute" thread, usually the "if you don't like it don't read it" rule applies - it's usually meant for a tribute to be sent to families or fans of the deceased. I remember specifically a thread that was a meant to be a tribute to a freeper's friend who was killed in an accident, and it was absoLUTEly trashed by people who just showed up to make crude comments about a dead person they didn't even know (motorcycles enrage some folks evidently). I just don't think it's right to mock someone's grief, or to mock the dead. Ask people's grannies, they'll usually say the same thing. And I'm not even that old...
I was raised up specifically not to speak ill of the dead - perhaps that's just southern, or old fashioned, but it brings BAD mojo on the person doing it usually. Unless it's Arafat, and I broke my rule on that one. I hope I don't get bad luck from it... :P
I was raised the same way. I had a brother-in-law die who was a real SOB to his wife (my husband's sister) and I felt no desire whatsoever to speak well of him after he died. I held my tongue but knew if I ever did talk about him it would not be out of a phony sense of respect I never felt for him in life. So here it is 10 years later and I still haven't talked about him which is my respect for those he left behind, not him.