He's the democratically elected President of the USA.  He said loudly and clearly during the campaign what he would do if elected.  Americans elected him.  He's doing what he said he would do.  What's the problem?  What?  You thought he wouldn't really do it?

IMO it's rational thinking.  The overwhelming majority of terrorists espouse some demented connection with Islam.  Why allow any more potential extremist Islamists into the country?