Trump has not said he intends to make Islam illegal in the United states. He has not proposed any political, housing, employment, benefit, or service related tests or discrimination against Muslim Americans. He has simply stated that bringing Muslims in from outside the country needs to be stopped until we understand better how to vet those coming in and determine better which ones want to kill us, and which ones want to come here to actually be Americans.
There is a sensible analysis of the entire Trump proposal here, not just the cherry-picked provocative parts.