Kill them with kindness

Describing polite, mannered, or dignified activities directed to someone who is curt, rude, or standoffish. This is a common practice when someone is rude solely to get a rise out of their target, or because they are being ordered to by someone else. The concept is that which such polite actions being reflected, the rude individual abandons the rudeness since it no longer gives the desired effect, or will enjoy the polite company and reflect it back.

My family can be a bit standoffish to new people, but you know, give them a little kill them with kindness.