Diablo 3 is a game that people had expectations for... right or wrong, one of those things was an endgame that would be enjoyable for a long period of time, as many people found Diablo 2's endgame. Catch is, you can't even see what Inferno is like until you've played and beaten Normal, Nightmare, and Hell, a task which probably takes most people well over 10 hours. So by your logic, by the time someone has played enough of the game to actually see what the endgame is like, they're no longer allowed to claim they hate it, even if the endgame is what they were looking forward to.
They aren't masochists, but WoW and Diablo 3 both require you to play for a very long time just to get to the parts of the game that you want to play. That doesn't mean you necessarily enjoy it if you play long enough to get to the endgame, that means that even if you dislike it you continue to play in the hopes of an eventual payoff... and for most people, the more time and effort you put into getting that payoff, the more bitter and frustrated you'll be if it never happens. So seeing people that played long enough to actually get into the endgame, see what it's like, and then turn around and say they hate the game is perfectly logical (even if the enjoyed the game until max level).
*shrug* I don't mind D3 too much, though my internet and Blizzard's servers together are too laggy for it to be playable, something I blame entirely on Blizzard for two reasons.
1) While I suffer lag with any online game, the lag I suffer with Blizzard games is worse than that I suffer with any other online game (and it's consistent in WoW, SC2, and D3), so even if it's not solely their servers, there's something wrong there that isn't wrong elsewhere.
2) Blizzard made the decision to require an internet connection to play, something that provides me literally zero benefit, so even if the internet problem were entirely on my end (and Guild Wars 2 and Torchlight 2, among many others, prove it's not), it's still their fault that the internet connection is a problem at all.
So I stopped playing D3 and started playing Torchlight 2 instead... and as a result, I doubt I'll buy the D3 xpac when it comes out. I put many hours into D3, and did enjoy it while I played it and it worked.... but I still wound up feeling very disappointed by the game, and would not recommend it to others.