It was perfectly appropriate.
Trump was trying to ascertain whether the boy (yes, I use that term to put him down, because he was a plant) was of SK descent and whose loyalties were still with SK.
If a woman in a Burqa stood up and started trying to “get the facts straight” regarding terrorism in Syria, it would be apropos of any candidate to ascertain whether they were from that country and had some personal, vested interest in asking the question.
WOW - it’s as if you hacked my computer and cut paste and sent before I had to - the same answer!! - Nice going!