Realistic dialogue is not necessarily good dialogue. Yes we all say “well” and “so” and “um”, but I get enough of it in the real world. I go to the theatre, see a movie or read a book to escape the real world. Good dialogue is concise dialogue. It’s not repetitive and it does not reflect subtext.
People rarely say what we think. We contradict ourselves all the time. That’s what makes us interesting. Your writing should not be a reincarnation of what you wished you had said in an argument. I’d much rather hear what actually came out of your mouth — as idiotic, inappropriate, or rude as it might have been.
Keep your characters real by having them put their feet in their mouths frequently. And then don’t explain their bad behavior or rude commentary. Let us try to do that!