following “i’m sorry” with “but” usually means you’re going to follow it up with something offensive like “i told you so” or “that’s just plain stupid.” in that case, you’re not actually sorry. you’re just opening with that as a way to sort of excuse yourself for the dickhead comment you’re about to make.
it doesn’t make you any less of a dickhead though. it actually makes you a bigger dickhead because the technique gives you an air of superiority or condemnation. plus you’re lying through your teeth. if you were really sorry, you either wouldn’t make the offensive statement at all, or you would approach the topic without that snobby tone.
if you’re really sorry, just say it and then promptly shut your fucking mouth.