What Are Some Good Comebacks For Being Told To Shut-up ALL The Time?

Don't waste your energy or emotions on a comeback.  

Just walk away, and find friends who respect you.

If someone feels enough contempt for you to tell you to "shut up" -- especially in front of people -- then they are NOT someone you should feel any respect or liking for at all.

Walk away, and hang out with other people, or with the few members of the group who aren't rude to you.

But -- since I suspect you won't listen to this advice, which I SWEAR is good advice! -- you could try, "Wow... You sound just like my mother... Your maternal instincts are a little out of control, don't you think?" and THEN walk off.