And it's an historical fact.
When a Christian puts their religion first it can mean something different than a Keith Ellison putting Islam first. For reasons that are sadly not obvious to all of us. For Cruz and the majority of Christians in this country it means simply that their faith is in God before government. Moreover, there's not much in the way of practical effect: in other words, apart from how a Christian congressman would vote on abortion issues it's not like they stand out from the crowd.
But there are many millions and probably billions of Muslims in the world that not only put their religion first, they believe, quite strongly, that their holy book mandates that their religion serves as a corpus for civil law. Saudi Arabi is a glowing example of where Islam IS the government. Iran would be identical except they are Shia instead of Sunni.
So yeah, when a Keith Ellison says he puts Islam before the government it should raise a few antennas---it means at least a few people are paying attention to what's going on in the world and/or they aren't blinded by political correctness.
When Ted Cruz says he's a Christian first, it's ho-hum; there's millions of us and things are going just fine unless you're in the market for a gay wedding cake. And last I looked no one is having limbs lopped off for shoplifting, or beheaded for blasphemy or other barbaric et ceteras.