Explain the reasoning for the reaction to chemical weapons in Syria?

Because you can kill an awful lot more people with a sprinkling of nerve gas than you can a ballistic missile or artillery shell.

It's why chemical weapons are considered WMDs.

The reasoning is simple.

We have an inexperienced know nothing who opened his naive cake hole and said "cross a line". Now, just to satisfy HIS ego he has to prove he is in charge. He has NO support, neither from allies or from the citizens of this nation. He is risking enormous consequences if he miscalculates (which he has done many times already - think stimulus for one). And even if those consequences don't come to pass, BOTH sides of the Syrian conflict HATE the United States. He isn't going to change that. Look at the mess he has helped make out of Egypt and Libya.

This is all because an egotistical loser lib lefty HAS to save face at all costs. Consequences be damned.

And we have 3+ more years of this loser.

We are so screwed........

This is actually a very interesting question with a really interesting, but probably unsatisfying answer.

In the lead up to WWI, war was romanticized. Young boys were reading about glorious cavalry charges, winning honor in battle, and being a gentleman. Try to put yourself in the mindset of a Romantic-era gentleman who spent his life reading about the Napoleonic wars. Put yourself in the mindset of a 20 year old living 50 years after a time when men dueled each other over disputes of honor.

During this time, and for a few thousand years before this time, poisoners were reviled. Poison was the weapon of a coward hiding in the shadows. A poisoner wouldn't duel you. They wouldn't make their intentions known, they wouldn't give you a shot to settle your disagreement like men, they would simply kill you in secret. Poison was a woman's weapon.

Gas in WWI wasn't especially destructive, it was just disturbing as hell to the psyche of the romantic-era gentleman. Men seeking honor shouldn't use a woman's weapon. There's honor in being shot by a man, there's honor in being shelled by a man, there's no honor in being killed by a poisoner. It was so disturbing that gentlemen the world over agreed to never use such a cowardly weapons again. In WWII, it was never used by any side.

We're not romantic-era gentlemen, so the idea of death in 45 seconds by asphyxiation being worse than dying after spending three days with a slug in your lower intestine is a foreign concept.

While I don't agree with attacking Syria, the UN and other countries are considering it because what Syria did infringes on the Geneva convention. They cannot use biochemical weapons, let alone on their own people. This is wrong and evil. So countries want to stop it and make sure these horrific events never happen again

Because if the world cracked down on killings with bullets, they'd have to boycott Detroit, and that would be racist, yo!

People in general have been viewing chemical warfare as abhorrent since WWI. You may disagree.