Donald Trump's signature proposal on stopping or restricting Islamic immigrants is, like his other proposals, unclear because it changes and is not fully described. Is it possible to reliably identify who is Islamic? I am skeptical. What is the most effective way to the vet immigrants? Do we have good reason to think that fewer immigrants would be effective in preventing homeland attacks? How do we measure the additional risk of threat of attacks from accepting more immigrants? What level of risk should be required to justify an immigration shutdown? What are the repercussions? I do not know and it is because I am an ignoramus that I am inclined to refrain from discussing complicated issues like this.
Nevertheless, I can say, based on what I have read, that there is solid evidence of ongoing efforts to carry out attacks in Europe, and to encourage lone wolf attacks, that rely on religious belief based appeals. Therefore, a review of immigration policies that includes considering options to take into account religious beliefs when vetting immigrants is not automatically an example of racism, or a violation the Establishment Clause, or Islamophobia, or siding with the religious right, or whatever the hell the latest knee jerk invective is favored by those who seek to try to shut down discussion. When we set our immigration policies we should do our best to take into account the needs of refugees in addition to the risks and try to strike a sensible balance. If more people die in car accidents every week than are killed by immigrants every year then restricting immigration is probably not justified. Otherwise, in the long term, if reduced immigration succeeded in preventing attacks then we could end up accepting more immigrants than we would have if we had instead experienced major attacks and reacted by shutting down immigration.
Trump is terribly wrong in so many ways about so much, which appears to tragically be an unavoidable result for any Republican presidential nominee in 2016 given how that demographic votes. The bombastic Trump, given his populist track record, and his divisive rhetoric, taints any proposals he makes while engaging in election year posturing in front of the electorate. A partial immigration slowdown that tries to reduce risks from accepting immigrants is not inherently crazy or irresponsible, although a policy that rejects everyone who is Islamic, as suggested by Trump, is difficult to justify. Being Islamic says too little about the person. But if there is a strong enough positive correlation between criminal violence and being Islamic among immigrants, or good evidence of ongoing dangerous plots and capabilities, then it may be justified to make that one of the considerations.
While Clinton currently expresses opposition to restricting immigration, if the context changed so that risks from immigration became larger in the future then I would not be surprised if she reversed course. I would prefer that she would say now, as a candidate, that reviewing immigration policy would be one option she would consider in the event that violence by immigrants became a substantial problem. I think Clinton has a track record of being pragmatic and thoughtful with respect to policy advocacy, more so than any other candidate, including the third party candidates. Regardless of what anyone thinks about the other candidates, this election is between Clinton and Trump.