Minus genjutsu, it'd be safe to assume that guy = madara, right?
Not exactly. By disturbing your chakra flow, you can break Genjutsu. Breaking open the gates causes massive eruptions of chakra in the circulatory system of a ninja, which would logically be sufficient to break a Genjutsu. Variables such as which gate one opens and the Genjutsu used all plays into the process. Though, Madara's Genjutsu was never notable compared to those in possession of top tier Genjutsu, such as Itachi and Shisui. Infinite Tsukiyomi is one of the only Genjutsu where opening the gates would be insufficient to break the illusion.
Edit: Gai does have ways to counter any attempts of Genjutsu, but Mugen Tsukiyomi is a different matter entirely. Also, anything less than Gai using the 8th Gate would be insufficient to combat Madara.
