Moderation, but in moderation :)

I draw the line at personal attacks and fighting words. Disagreement that furthers the discussion is one thing – but going after the PERSON is different.

I delete about 1 in 300 non-spam comments on these grounds, so I clearly allow quite a bit, especially on political debates.

You are not bound by the 1st amendment (which states that congress shall make no law …) – you’re well within your rights to censor as you please (although it’s prudent no to go overboard).