Trump Immigration Ban

Why are people upset over President Trump’s making it harder for terrorists to come into this country? ISIS says they will infiltrate refugees and sneak into our country to kill and maim our citizens. There are already people here who were converted to terrorist sympathies that have shot, bombed and driven over our citizens killing and maiming as they did so.
 
Why in the world are people against stopping this? Jews in WWII and Japanese camps were treated wrongly but they hadn’t said they were coming to kill and maim us. However when Jihadists tell us they’re coming it makes sense to take more time and vet them properly. I’m sure Germany, Belgium, France and others wish they’d done so.
 
Why didn’t Congressman Chuck Schumer use dead victims from Jihadist slaughters for props for his comments instead of a Muslim family?