At the other side of the argument I know 2 people who were jailed for very, very serious crimes, both were unjustly treated by the courts imo.
Its a very dodgy area, The "paedatrician" post proves that there are too many thick, unintelligent halfwits willing to make a lynch mob over a rumour.
I think rather than take the law into your own hands, the emphasis should be on the courts and judges handing out punishments befitting the crimes.