"Would they have been tortured if they had fulfilled their military obligations?"

He was tortured because they thought he was connected to terrorists not because of so-called military obligations to Syria.

"Why did he and the others keep their Syrian citizenship?"

Probably for the same reason I kept my U.S. citizenship. Thats where I was born.

"And what is the status of a non citizen at an international airport in the US?"

He was not a non citizen, he was a citizen of Canada.

"And when did Canada start giving shit away?"

We will give you shit anytime you ask for it.