To slap someone is always BAD and is much worse than a simple insult. I would never say "slap the taste out of". That doesn't make any sense to me as an American. We may "slap someone silly". (slap them repeatedly) A lady may "slap a man" (once) if he insults her. An abusive husband may slap his wife around. (slap her repeatedly)

I think I heard this on TV before... I don't recommend using it. I've never heard someone using it in real life, anyhow. 1) It can used as a simple threat, after you're annoyed or you cannot tolerate what someone is doing and wish them to stop. (What Kenny said.) 2) If you're about to slap someone very hard. It's similar to "I'll kick you into next week." That's about all I can think of. But, still, I think leaving agressive behaviour out would be a better solution to any situation.

From the Net> Phrase used to try and get someone to stop or not do something that you really do not find appropriate. Boy, if you don't stop hitting your sister I am going to slap the taste out of your mouth.