Not at all - your professor seems not to see muslims here.
Muslims colonised Indonesia and conquered India. They did not colosided America or China because they didn't have to. They simply had best trade sources or they controlled only way to deliver them. :)
They also converted large parts of Africa. Anyway I don't think that the Muslims didn't need to colonize/discover America, they simply weren't in position to do so, and they did not know a route there I think. If you just sail without knowing what you're doing and where you're going you won't find anything. Columbus believed the earth was round and believed he could get to India by sailing west, problem was a continent sort of blocked his way, but he did believe he had found India I think.