Obviously, somebody who dislikes games published by Sega, either with or without good reasoning.
Sega Slayer is a sega hater.
Most of us hate Sega because we actually owned and LIKED playing the games on its consoles (most of SEGA's games rock), but then got screwed over because we bought the consoles just before;
(a) the company ceased support for that particular console in order to concentrate on whatever new project they would eventually fail, or
(b) the company bailed out of the console business just to cover its debts from Example A.
We aren't SEGA haters because we think the company makes mediocre-quality games. We're SEGA haters because we wasted our valuable cash investments buying product failures from the company over and over again.
Someone who hates Sega, either because they are ignorent, think they make crap games, or more commonly, hates sega because they fail to accept their own responsablility for buying a console/add-on which then failed.
Sega didn't intend for the mega cd, 32x and saturn to be failures! It's just people didn't buy them, so they failed!
A sega hater bought a mega cd but the mega cd was unpopular so they stopped making games for it. The sega hater then blamed sega because their console was unpopular.