I don't mind people being enthusiastic about a culture or a country, so long as they don't go from mere enthusiasm into irrational mania. After all, I'm a big fan of medieval China, though you'd never know it to look at me and I don't spend hours gushing about it.

The wee</>aboos who really annoy me aren't the ones who insist that Japan is teh best countray EVAR - though they're bad enough. No, the really irksome ones are the kind who insist that everywhere else, especially the west, is teh total sux0r in comparison.

A pet peeve example would be "knight versus samurai" threads that crop up now and then. I've studied and trained western martial arts, and have a reasonable understanding of feudal martial culture in all its forms. So it really bugs me when a clueless Japanophile starts frothing about how knights were stupid filthy Christians who had no training and no skill and just wore armour and bashed at their enemies widly until they died - while Samurai were all unsurpassed warriors who trained for decades and had unbeatable sword skills and KATANAS THAT CAN CUT STEEL. Ugh.
Being ignorant is one thing.
Condemning something because you're ignorant of it is something else entirely.