My Master, who is my (now) Fiancee of two years, and I have MUCH respect for each other. When he calls me Slut, its normally when we play but normally I am "Pet" and SOMETIMES "slave" ( although he NEVER calls me slave in front of my girls...) when we are playing. Slut doesn't bother much really because if ANYTHING, I am BY FAR NOT what the definition of what a slut is. The ACTUAL definition of one describes that of a "sexually promiscuous woman" and I am not. Unless my Master desires me to sleep with or play with another or decides to share me, I wont even be a slut then because it is HIS wish.
He is my TRUE Master (and love of my life) and when he calls me "slut" sometimes I smile because if anyone else were to call me that, they'd get knocked on their asses, either by me ( who Master has trained in self defense) or by Master who would knock their teeth down their throats for disrespecting his property.