If you truly know that a person hates the Jews and denies their rights, or just know any other evil the person does continuously, you have no obligation to respect him. The Shulchan Aruch says "Even a pagan old man must be respected, EXCEPT IF HE IS AN EVILDOER.
However I think you cannot assume he is evil just for calling himself a Muslim. Anyway how do you recognise a Muslim un the street?