Look, let's go back to the start. You said, and I quote:
However, with a religion like Baptist, where there is no infallible authority figure, if a Baptist minister said homosexuals were not allowed to be Christian, it has no relevance on Christianity itself.
The same goes for every current religion out there, at least the common ones that I'm familiar with. With TWO exceptions: Catholicism and Islam. In both of these religions, the authority figures are infallible and thus do play a very critical role.
The same cannot be said for Islam who still has infallible authority figures, and these authorities dictate Islamic law.
The ONLY religion where true, infallible authority is found (currently, and ignoring Catholicism for this example) is in the Muslim faith. These infallible men DO define what Islam believes. They CAN make new laws. They DO have actual, unquestionable authority over Islamic doctrine and interpretation.
Now, it is certainly possible for a Shi'ite Twelver Muslim to identify you, me, or (more plausibly) a Grand Ayatollah as being the Mahdi; just as it is possible for a Catholic to identify me as the Pope; a Protestant to identify me as the Second Coming; or for a Jew to identify me as the Messiah.
But there is nothing in those religions that says that you
have to so identify some random person such as me as the Mahdi/Pope/Second Coming/Messiah.
And in fact most Shi'ites, and indeed Protestants and Jews, do not make such an identification. And if they did, they still don't have to.
So I conclude that there is nothing in Islam that makes Muslims have to follow a leader --- and the mostobvious and practical proof of this fact is
that they don't.
You remind me a bit of creationists talking about genetics. You're using every argument you can to prove that no matter what happens in practice something completely different should happen in principle.
Well, it doesn't. Which kinda proves that the principles that you have laid down for Islam are not the principles followed by Muslims.