No, the reason it is (or should be!) frowned upon is because the labeling of an entire religion -and by association the entire range of its adherents- demonstrates ignorance of its different interpretations.
As Hax has helpfully outlined, there is no single monolithic interpretation of Islam -and there is a real multitude of views within it. As ever, it's the bad bits that get picked up and denounced -which I think is right to do, but it is absolutely wrong to surmise that the whole of Islam is thus.
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