If you are a foreign policy expert in here raise your hand......
I am waiting..........
Fact of the matter is Counterinsurgency operations have so many different dynamics to consider. Based upon all the operational factors that are in play, a military option may indeed be the best option available. The primary intent in Syria should be the fight against ISIS (regardless of who supports/supported them and the other actors who are agents for instability in the region). Failed states have a habit of spilling over across borders. If the neighbors of said failed states can not provide a secure environment for their state, then the violence and instability will follow into that country. Now you don't have a failed state, you have a regional security issue. Issues with regional stability is a problem for everyone in the international community.
inb4 the Russian apologists say we will attack Russia. inb4 the liberal blame Trump for the issue Obama created. inb4 the libertarians and An-Cap crowd say we should stay out of it because it doesn't directly affect America.
The fact of the matter is that whether or not we want to get involved we have to get involved. Historically speaking, when we have left failed states alone to deal with asymmetric actors, we have dealt with it later (i.e. GWOT). At this point, it doesn't matter if Assad is a bad guy. You can hold states accountable. What is much worse is a group of fanatics that want to destroy the western world, that cant be held accountable. They have no legitimate borders, economy, or assets.
I am a libertarian on most issues minus foreign policy. Isolationism does not work if you are a super power. You have an obligation to ensure peace and tranquility in the international community. The reason being is that it all affects your domestic policy and your economic system if not. Trade partners are affected. Refugees wanting in your borders because of how your country is set up. There are a plethora of different aspects that affect us just in this one situation. Having spent the past 15 1/2 yrs in the intelligence community has taught me a great deal on geopolitics and counterinsurgency theory. I am all for ground troops in Syria so long as we are fighting ISIS. I will volunteer to go, if given the opportunity. The only opinion I will half way respect in here on this issue is YorkVol. He has probably forgotten more than what I know when it comes to intelligence and geopolitics.