mosschops i don't know if this will help but i am of the same school of thought as you and caligula: fight to the death alongside dh whether he is right or wrong (then in private talk to him about it if think he is wrong type thing)....
however, dh is more a loves me, is loyal but has this sense of fairness thing going on where irrational loyalty is difficult for him...
is it possible that your dh thinks that as he has reprimanded his friend it would be unfair to cut him off completely? if he thinks this he may feel that you're being really unfair in asking him to do that....
does it have to be about how much he loves you? could he not make clear again to all of them that the guy was offensive and in the wrong without not seeing his friends???
am i making any sense at all? i totally get where you are coming from, and have been there myself, but am also trying to leap into your dh's consciousness too???