Why not? So what kind of people do belong in the US? Illegal, border-hopping Mexicans, I am guessing?
And what's wrong with being anti-Israel? And what's wrong with being racist? Serious questions.
Have you asked yourself why?
These seems to be very strong sentiments. I believe that people most likely have good reasons for them. Seriously, who goes around chanting they want to "purge" certain people without having good reasons?
It's your country, you can let in whoever you want. But, you also can't say that yours is the land of the free or whatever mantra you Americans like to chant. You will only allow people of a certain political persuasion into your country.