For some people, it can sure be. Whether it's a reasonable reason is another question, but to them it must feel like one if they don't buy a game because of it.
To me? Depends, I suppose. I haven't had to make the decision even once yet, so it's hard to tell. In most cases I'd probably whine about it, but I don't think there's a lot of cases where it'd actually make me not buy the game.
EDIT: And just for the record, I don't consider localization censorship, but I do kind of despise a lot of things that are considered localization that are also considered censorship by some. Unless the thing flies way, way over my head without extensive localization, I don't want it to be too thoroughly localized. Heck, I don't even want a single game to be voice-acted in my language, and I don't actually even want a single game to force my to use subtitles in my own language. In a lot of cases, I don't even want games to be voice-acted in English unless that's the original language. I want the experience to be as close to the original experience as reasonably possible.
