A cop-out? Not really, it's playing with the expectations of any listeners. They think they'll get "shitty" and instead they get "slippy" - and then later maybe you might use "shitty" which would by then be a surprise, precisely because it hadn't been used before. In a way the effect is one of reimposing an eroded taboo, and then breaking it.

Two for the price of one.

How'd that for a retriospective rationale?