Simon the allusion is in the form of words and the exclusion of the possibility of there being such a thing as a "good" Muslim. It's disgusting rhetoric.
In the 19th century Americans discussed whether there was a useful distinction between good and bad Indians, hostile and reservation Indians. Some expressed the view that there was no meaningful distinction and that the "only good Indian is a dead Indian".
Now some people are arguing that there is no meaningful distinction between violent extremists and those who practise Islam peacefully. Even going so far as to say the only "good" Muslim is an ex-Muslim.
If others can't see the parallel or why it's disturbing there's not much more I can say.