On one hand, I share many of the question you and the prof bring up, for the same reasons. I did at the time and I still do.
On the other hand, rhetorically asking, what good is it going to do to question the overwhelming conclusion? The conclusion that has been reached is the one we have been instructed to accept. You and I are never going to get better than 6th hand information.
Syria Claims US-Led Coalition Strike On ISIS Chemical Weapons Depot Has Killed Hundreds | Zero Hedge http://www.zerohedge.com/news/2017-04-13/
If this really happened today, then it proves ISIS has chemical weapons.