I have to say that I don't really like it. Sometimes it doesn't bother me... I've definitely called clients "dirty little sluts" or "naughty fuckers" during bookings if they've hinted that they want it. If the guy is overall cool and it comes up during a hot part of the booking he can say "you dirty slut" and it might not bother me. But if all I've done is gone down on him and he's looking at me with a smirk and starts saying "You dirty fucking slut" it really bothers me.
I suppose I am a dirty fucking slut. I mean, I do "dirty" things (anal, CIM); I am fucking them; and I suppose the definition of "slut" is someone who has sex with a lot of people. But when a client is saying those things I sometimes get the feeling that he's expressing contempt for women via me (or maybe just contempt for me) and I don't like it.
I generally don't say anything because I don't want to come across as a huffy, up-her-own-arse wannabe "courtesan" but I have sometimes stopped what I'm doing, looked at them a bit puzzled, and ask, "Why did you say that? Have I upset you?"