It's a legitimate issue. For whatever reason, people have a hard time admitting that external factors matter. The prevailing attitude seems to be that whenever these are brought into the picture, an excuse is being smuggled in.
I guess the problem is how to fit the altitude-preparation into the picture without making it an excuse. I'm pretty sure Werdum is just a better fighter, having seen the fight...BUT. I'd be lying if I said I didn't want to see every fight with both fighters at their best. And it seems Cain wasn't. But then---neither was Werdum, IMO. He was just better-prepared than Cain, even if not at his own best.