One can believe that anti-Semitism is a big problem on college campuses, and that it is primarily coming from the progressive left, but also believe that Trump's proposed Executive Order defining Judaism as a "nationality" is a really bad idea.
Not only does that nationality language echo the language of anti-Semites on the right, it runs in the face of the self-conception of most Jews, which is that Judaism is a religion, not a nationality. The EO would also, in my view, criminalize the free speech rights of BDS activists. Again, one can, as I do, find their ideas and proposed policies deeply troubling and sometimes anti-Semitic, but also believe that they have the same rights to political speech that everyone else does. The EO would limit those by more or less declaring all anti-Zionism to be anti-Semitism, which it most certainly is not..
At some level, this whole thing is concern trolling by the right. If Trump wants to help Jews, he'd be much better off addressing things like the incident in Jersey City yesterday, or the continued anti-Semitic violence in Brooklyn. Worry about people getting shot in kosher markets and Jews getting beat up on the street before you ham-fistedly "help" Jewish college students by adopting a strategy of anti-Semites on the right.