Shekermoochlat, I agree that amateurs shouldn’t be marbitz Torah, and if you wanted to be makpid that all rebbeim know gantz Shas and poskim, I’d be maskim in theory, but we would have no rebbeim. So the question remains, why davka should a rebbe need to know the parts of Shulchan Aruch needed for s’michah more than anything else, and the answer is that he doesn’t; that’s completely arbitrary.
Avi says it didn’t sit well when rebbeim were called mister (something that if true, was before my time). Of course it didn’t. Torah teachers deserve a title of respect.