for me it's not happening ...you can lick it and tickle it oh hell yeah.....is it wrong? no... if its what he wants then its right... does it make him less...no!....unless of course he wants you to strap him down and fuck him...then yes that would make him less.....

this can be done as punishment for you as he has you lick his dirty asshole and then clean it by fucking him... it can be used as humiliation as he has you lick it and fuck it with your fingers and then lick your fingers clean.... it can be done while in a 69 position while you suck his cock you finger or fuck his ass as he does the same to you....

if you still can't wrap your mind around being able to do it with out losing respect for his Dom/Master...then take it out of play time and move it to the vanilla sex time between you ...Be safe and play well