Errors in Speech

Putting one's foot in one's mouth is quite a simple task, yet there are some people who almost make an art of it. It is as if they never know when to be quiet. Then they see their mistake, or more than likely, see it on the other person's face, and try to correct their error, and end up putting both feet and at least one hand in there as well! What is a polite way of saying, "I'm sorry, but you need to be quiet?" Or, "I don't believe that was the right thing to say?"

Sometimes it would be so nice to be blunt. Don't you think? Or is it just me?