Thanks for the translation!
I don't know what the raws say, but shouldn't this either be "formerly a professor" or "a professor emeritus"? Afaik, the honorary title of emeritus/emerita generally isn't revoked after being granted to a retired professor of certain rank.
It made me read it as if there was some huge unspecified scandal that forced them to revoke it.
I'd have translated that line as follows:
"Professor McLegan is a professor emeritus at Minerva, the mage training institution!"
Actually, a more literal translation would be this:
"Professor McLegan was serving as an honorary professor at Minerva, the mage training institution!"
The term in question is
名誉教授 (meiyo kyouju) in Japanese, which literally means "honorary professor," a position that he had been granted in the past and continues to hold. This is indicated in the past progressive verb 務めていた (tsumete ita), which means "was serving" or "had been serving." The literal translation is cumbersome, whereas the one that I suggested sounds smoother.
As for the old professor's name, it's マクレガン (makuregan) in the raws. The "r" sound in Japanese is actually halfway between "r" and "l" and is difficult to pronounce properly for non-natives. I'd translate that as "McLegan," but that's just my personal preference.
The part about him being referred to as a high mage puzzles me though. That wasn't in the raws.
That said, I know only too well how difficult it is to translate a chapter. I'm just glad I get to sit back and read one of my favorite manga.