Last month we discussed Wikipedia's policy "Civility" directing editors to get along with each other. Closely related is the policy "No personal attacks" prohibiting specific antisocial behaviors.
A favorite saying of Wikipedia editors is "Comment on the content, not the contributor" and it's well-worth keeping in mind. The purpose of Wikipedia is to build an encyclopedia, so it helps to keep the focus on the specifics of any disagreement. No need to make it personal.
On Wikipedia, a personal attack need not rise to the level of a legal threat, and the policy page includes a substantial but inexhaustive list of actions commonly understood as unacceptable.
But really, if you stick to common sense and apply the Golden Rule, you should be fine. The downside is not everyone does, and sometimes dispute resolution is necessary—but more about that next week.