You'd have to define exactly who you are at war with and how you plan on screening people using that definition. Trump's ideas are ridiculous, as are many of the posters on this site on this topic. If religion was some big defining criteria then Catholics would have been segregated and banned from immigration centuries ago.
I fully understand this situation. And I'll again ask the same question. What exactly has changed in US immigration policy the last 20-30 years ? Why are Trump and numerous posters on here claiming that it's an "open border" policy ? Is it not true that quite the opposite is true, that since 9/11 that US borders are more closed then ever ?
Governments cannot operate on emotion and bluster. Laws and policy have to be fairly designed and not discriminate based on ethnicity, religion, skin colour. You cannot judge people based on the most evil factions of their group, and quite frankly many people are being grouped into groups they don't even belong to or believe in. It all gets pretty silly when Trump starts questioning the ability of the judge based on their parents birth place. How many on here would want their career or personal life judged on anything to do with their parents ?
On this shooting, the shooter absolutely hated gay people. I am reminded that occasionally abortion clinic's in the US have had incidents because highly religious ( supposedly Christian ) shooters hated the people at the clinics. The fact 50+ people died is more reflective of the high powered weapons that are easily accessed in the US these days.