There are a few things that people of bygone ages have fought to eradicate from human history.
Slavery, for example, is something that was eradicated from most civil society in the 1800's, with the last country officially allowing slavery being Saudi Arabia in 1960.
These are meaningful victories in the progress of humanity. These are milestones in a human history that at one time glorified in crucifixion too, but learned that this is not how we ought to define ourselves at a certain point too.
Chemical weapons likewise is an evil of WWI that civilized people everywhere agreed was something that people ought not fight wars with.
This is not something that either Obama or Trump differ on. As much as Obama was loathe to enter into the Syrian theatre, and as much as Trump spoke out against that too, the agreement that Obama set in place with Russia (back in the days of the red line in the sand), failed.
There was an agreement that America set into place, that was binding on all parties, and it was broken.
Now I suppose if China or some other country decided that race-based slavery was alright, there is not a lot that anybody could do other than register their displeasure. They could go 'tsk, tsk' as a means or registry, or they could stop trading, or anything up to nuking, really.
Maybe nuking would be too much though, and maybe a 'tsk tsk' would be just another way of saying that nobody gives a dam.
That is the situation that Assad has put the world in by continuing to use chemical weapons. How can the world register their belief that this guy is a monster with enough passion that people everywhere understand how horrific this kind of warfare is, even in comparison to everything else that has gone down? How can America convince the world that they are serious, if the agreements they sign onto are disregarded as mere paper from a paper tiger?
If by this action, the world gets the message that Assad is a monster from a whole new level of low, that is what this kind of message was meant to accomplish.
'Tsks, tsks' and red lines in the sand are just not enough to send that kind of message anymore.
