To call it stupid is to say that every fashion is stupid. It's just a fashion. And fashions are just opinions. And everyone is entitled to an opinion. I don't particularly think that anyone else's opinion holds any less merit than my opinions. They're only opinions after all.
No, calling it stupid isn't saying that every fashion is stupid. It's a statment (of opinion) that this particular type of fashion is stupid. So if Perk is entitled to have his opinion on fashion, aren't people who think it's stupid entitled to their opinions as well? After all, under your logic, nobody's opinion holds any less merit than anybody else's...
(Incidentally, I thoroughly disagree with that statement. In many situations, where an opinion is held contrary to established facts and evidence, then it holds less merit to me, particularly when the person spouting the opinion has some type of influence on less informed people or when that opinion is spouted as fact. But that's a wholly different philosophical discussion irrelevant to Perk's grill.)