STOP DEFENDING YOURSELF. I haven't used sin for a while so I haven't had someone call mb bm (lol pun) but when they call life tap / resist stack / absorb stack/ smiting / charging bm in PUB DUELS I just say I don't give a ****. Really, all this bm crap has gone too far. OMG HE BEAT ME BM!!! OMG YOU NOOB STOP YOUR BM. Even if I meet people who really bm against me, such as nk or pot drinking, I don't complain. I just duel their way and beat them (if I can't I just leave lol). In PUB games anything goes. If he pots I pot. If he nk's me I nk him. Just tell them to mb themselves and stop crying.
In privates, however, that's a different story as people make up rules for strict dueling.