Unless a flagged forum post is actively advocating physical violence against another party, it should not be edited or removed.
Censoring opposing points of view, no matter how disagreeable or offensive some mind find them, is not conducive to promoting respect and mutual understanding. Censoring does not lead to enlightenment, it only breeds contempt and resentment.
That said, too many forum threads devolve into name calling, innuendo, and personal insults. Agree or disagree, we should maintain a respectful decorum, and address other forum users no differently than the way we would address them in person.
For viewing content that is inappropriate for users under 18 years old, some websites require signing in to confirm age before controversial content can be viewed. I think a similar feature should be implemented on these forums. Controversial posts should be allowed to remain intact for those who wish to view them, while simultaneously allowing others to bypass them who do not wish to view them.