I think that, more than anything else, he hates accurate n64 emulation because he's the author of a lot of 'improved' texture packs for n64 games that's the main point, I think
and apparently he had years ago a bad discussion with someone on a MAME-related board where he got ridiculed about accuracy. this by far predates his work on vba-m. I was in touch with him at vba-m time, and I spent some time writing comments on his blog about accuracy, trying to make clear the flaws on his critics. but he already hated MAME/MESS even if no gba driver existed officially at time
EDIT: and concerning hate for byuu, he got banned several times from BSNES boards because he can't interact in a civil way with someone else
