You're not reading my posts, or are attacking your Straw Liberal, or something.
You can attack a person's particular viewpoints/opinions, sure. If there's a Muslim who's arguing that women should be subservient, that's guy's a misogynist. Criticize away. Literally nobody is arguing otherwise. That's the complete fiction you're inventing, to be aghast at.
Where the line gets drawn is when you attack everyone who shares a superficial similarity in another respect, by claiming they all share that one dude's opinion because of that unrelated similarity. For instance, when you claim "Muslims" are misogynists. Ignoring that there are many Muslim women advocating and working to expand women's rights around the world, just by way of example. You're being prejudiced and attacking people who AREN'T misognist, because of a shared faith they have with some people who ARE.
It's exactly as ridiculous as if I argued there was a "cultural problem" in "white society", which means that "whites are racist". Because hey, look at the KKK, and the racism in the USA, and plenty of other citable examples. Is that a fair argument? Of course not. It's blatantly racist, on my part. But it's the same faulty logic used as when people claim they're just "criticizing ideas" when attacking all Muslims for ideas they do not all share.
That is the prejudice. You're targeting people who DON'T share the beliefs you claim to have an issue with.