my little girl's very first compound curse :)

i forget what i was doing, but i was at the dining table, phx was at the laptop, and LB was in the hallway - from where we heard her say "I can't get off my fucking shit sock!"
we're like "whaat?" to which LB repeated the aforementioned obscenity. it was shocking, and we wanted to laugh, kinda, but i dont think we did. phx helped LB get her sock off, and we figured we really gotta curb my, er, our cursing again.
which brings me to asking again - what's wrong with cursing? what happened, somewhere along the line, that has made some words "Bad"? this seems to have occurred in most human cultures - but why? like - what the fuck?