Smiling and laughing can be a reaction to uncomfortableness. It used to bother me more, but now I just assume that is why. They don't want to be offensive but don't know how to respond. What does upset me is when people try to finish words for me. Close friends I will mention to them that it doesn't help and actually does the opposite. Otherwise I take the passive aggressiveness approach and ignore them and finish anyway. If someone is being a dick about it, you can always go with "p-p-p- fuck off." 😜