Many Democrats use 'unconstitutional' rather broadly to refer to anything they don't like. Senator Charles Schumer (D-NY) apparently favors this broad (mis)use of the term. He claimed -- wait for it -- that President Donald Trump's temporary ban on Muslim immigration from seven Muslim countries is "unconstitutional" because it applies a religious test.
But of course it isn't. In Article VI, paragraph three of the United States Constitution we read that "no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States." This has nothing to do with immigrants; it pertains to citizens who seek public office. (It is also worth noting that the clause says nothing about the states; it pertains to seekers of Federal offices. See here.)
So it is clear that Schumer made a false statement. Did he lie? Did he knowingly make a false statement? It is a good bet that he did given his leftist agenda. And he thought he could fool us, too.
It is plain, then, that there is nothing unconstitutional about applying a religious test to immigrants. It might nevertheless be argued that a religious test is being applied, unconstitutional or not, and that there is something dubious about this. "It is not who we are," some bien-pensant liberal will gush. But is the test religious?
Bear in mind that Islam is a hybrid worldview: it is as much a political ideology as a religion. The reason Muslims are singled out and subjected to a test for immigration-worthiness and found wanting is not because of their specifically religious views but because of their political views. As ought to be clear by now, Islamic law or Sharia is incompatible with the values of the United States. The state needn't care about anyone's views about abstruse theological questions such as the Trinity, the divinity or non-divinity of Christ, the exact mechanism of divine revelation, etc. But every state has a right to defend itself against subversive elements.
"Is every Muslim a subversive element?" Don't be stupid.