even if people dont wanna talk about it, it's still a valid topic.
There is still almost no proof that Tobi is Madara.
His knowledge? With that whole thing about using the sharingan and rin'engan to read secret records, there could be a place he got the info from.
He doesn't HAVE to be obito, though. He could be shisui for all we know. Or at least his body.