I hope what this policy amounts to is declining visas to students who support proscribed terrorist organizations like Hamas and Hizballah, broadcast blood libels, harass Jewish students on campus, etc. I had a foreign (Pakistani) student tell me, to my face, "I don't like you because you're a Jew." -- in front of a group of mutual friends, who awkwardly laughed it off as if he must have been joking. It's _not_ about mere criticism of Israeli policy or war doctrine, and pretending it is seems to be a new popular misperception on both the far left and the far right.
This was a very real thing when I was an undergrad, and it's surely much worse today. I have family with long histories of attending Ivy League schools, and their seniors are no longer applying to those schools, entirely over antisemitism.
If American universities were 1/3 populated by, say, Russian students with a high propensity for harassing gay students, implying that all gay people are predators, etc., I think the left-leaning commenters here would take a very different perspective.