DaMoshe > So who actually has the right to lead the zimun?
I think that the kohen has the first right. In shul, he can not refuse and offer someone else the first aliya, but at home, he can let baal habais.
Recall that the whole thing is for darkei sholom (see Gittin), so that there will be less machlokes about priorities. Thus, if you end up accusing people of something, you are not doing it right.