Can I be the first person here to point out that
armed toddlers killed more people last year than extremists of any variety, and that the armed toddler threat becomes even more terrifying when you factor out right-wing extremists (who represent a significant fraction of terrorist murders in the US) and attacks from US citizens? 21 people are killed every year by armed toddlers, compared to 2 from foreign-born Islamic militants.
A threat that is not overstated is the risk to Muslim minorities in Syria and Iraq. Armed toddlers, lightning strikes, and even lawnmowers (a threat that dwarfs all previously stated causes of violent death in the US) are a trifling concern to a Yazidi in the path of Syrian civil war conflict, either from ISIS or from mortar shelling from the Syrian regime.
And, of course, as we consider who's being harmed by this ban, it helps to remember that the ban also applies to lawful permanent residents of the United States. The spouses of many --- actually, 3 in 4 --- American citizens are LPR non-citizens; they've lived here for in many cases decades but can't return back (or, at this point, ever leave to visit family). No American can look at that situation and call it right or just or tolerable.