Do you use off-topic (ad hominem) insults when you're mad at someone?

As in, you’re arguing with someone who’s overweight about politics. They start to make you angry after a while and then you begin insulting their weight. Do you find that you sometimes hit below the belt like that?

Do you think it’s something we all do or are there people who just don’t do it? Do you really try not to or do you not care?

I’m guilty of it in the past but I really try not to do that. The “bigger person” doesn’t do stuff like that. It only makes you look bad and seems to show a weakness in your ability to carry about a civil discussion or argument.