Destroying that person's online reputation - and offline reputation too, if the person's offline identity is known - with a variety of insults posted on top Google-ranking pages is revenge.
Only if it is done intentionally to harm them. Negative information being publicly available is a simple byproduct of transparency. It's a matter of weighing up the harm done to the person against the harm done to Wikipedia by being less transparent. Since we like Wikipedia and generally don't like to people we are blocking, is it surprising we choose what's best for Wikipedia?