For me the word 'slut' and any other words one might title 'dirty' are words that can be used between partners (be it vanilla or bdsm type partners or any other type out there).... and when they are used in this nature then these words are erotic between these people.

If a complete stranger in the street in real life called me a slut... i would NEVER accept it. I would never put up with it, because for me when it is being used in such a way then it is being used to offend and to degrade, in a non-erotic manner.

If my partner uses it on me - in the right context, then i know they do so with respect and with the knowledge that its use turns me on.

I guess thats what it comes down to - context for example If my boss at work called me a slut... then thats sexual harassment, but if my partner at home calls me a slut while we are doing something sexual then thats a turn on.....