Not all Muslims are terrorists, but most terrorists on the planet ARE Muslim, and are acting in accordance with the Koran.
The more terrifying thing is how many Muslims support it. Over a quarter of Muslims in the West support Shariah law, replacing liberal secular democracy with an authoritarian religious state that privileges Islam over all other belief systems. Two thirds of British Muslims surveyed said they wouldn't turn in a person planning a terror attack, so even the peaceful ones wouldn't stop the violence. Not good allies, that.
The vast majority of Muslims, 60-90% depending on the country, support killing atheists and those who leave Islam for any other religion, killing homosexuals and killing adulterers. Even the moderate Muslims say it is OK to kill your kid for becoming a liberal atheist or coming out as homosexual.
When the majority of a faith is antithetical to your values, it is reasonable to say they shouldn't be allowed to come.