1. Chemical weapons are worse than other weapons.
This is not the case. Death and dismemberment are horrific regardless of the weapon. No weapon is being used legally, morally, humanely, or practically in Syria or Iraq. U.S. bombs are no less indiscriminate, no less immoral, and no less illegal than chemical weapons -- or for that matter than the depleted uranium weapons with which the United States has been poisoning the area. The fact that a weapon has not been banned does not create a legal right to go into a country and kill people with it.
2. Chemical weapons use justifies the escalated use of other weapons.
Does shoplifting justify looting? If a Hatfield poisoned a McCoy, would another McCoy be justified in shooting a bunch of Hatfields? What barbarism is this? A crime does not sanction another crime. That's a quick trip to hell.
3. Important people we should trust know who used chemical weapons.
No, they do not. At least they do not know that the Syrian government did it. If they knew this, they would offer evidence. As on every past occasion, they have not done so.
4. The enemy is pure evil and will answer only to force.
The U.S. government and its proxies have sabotaged peace negotiations numerous times over the past several years, maintaining that Assad would have to step down or -- preferably -- be overthrown by violence before anything could be negotiated. This does not make the U.S. government pure inhuman evil, much less does it make the Syrian government that.
5. If you don't want to bomb Syria with one enemy's name on your lips, you hold the firm belief that said enemy is actually a saint.
This piece of stupidity gets people accused of loving and holding blameless the Syrian government, the Russian government, the U.S. government, ISIS, and various other parties. In fact, the reasonable thing to do is to hold all killers responsible for their killing because of the crime, not because of who commits it.
6. U.S. war-making in Syria is defensive.
This is the opposite of reality-based thinking as war-making endangers us rather than protects us. Someone should ask Donald Trump to remember the Maine. You may remember that Spain wanted the matter brought to a neutral arbiter, but the United States wanted war, regardless of any evidence. That's been the typical move over the centuries: careful maneuvering into war, not away from it. Trump, by the way, is already up to his bloody elbows in several wars inherited from Obama -- wars no less immoral and illegal slaughters because of their connection to either of those presidents. The question of who blew up the Maine is, at this point a truly dumb one. The important point is that the U.S. didn't want to know, wanted instead to rush into a war before anyone could find out. Typically, the desire to avoid information, and not some other consideration, is the reason for the urgency in war-making.
7. Peace was tried in 2013, and it failed.
No. What happened was that Obama and his administration tried to pull off the same stunt that Trump is trying now, and the public rose up and refused to allow it. So, instead of a massive bombing campaign, Syria got more weapons, more trainers, more troops, and a medium sized bombing campaign. That's very different from actually shifting direction and offering Syria diplomacy, aid, and disarmament.