2/ You wrote:

<<Muslim terrorism exists on a large scale throughout the world, including Europe. It's a significant issue.>>

No one disputes Islamic terrorism is an issue, but Trump/alt right exaggerates the threat out of, oh, I don't know: bigotry?

"Are All Terrorists Muslims? It's Not Even Close"

http://www.thedailybeast.com/articles/2015/01/14/are-all-terrorists-muslims-it-s-not-even-close.html

You wrote:

<<Actually, the concern about Muslim immigration from radicalized countries is based on concern for national security. If it were merely based on ideas about race or religion, I'd be agin' it.>>

It's all three.