Any well trained military unit will be trained and equipped to deal with them.
I don't accept that this point always holds. And not all armies are well trained and equipped.
During the cold war the Soviets developed the Novichok agent - something that the US could not necessarily defend against. If soldiers are wearing gas masks and protective suits, they are less agile and less effective in using regular conventional weapons. This provides the enemy with a tactical advantage. And given that chemical weapons have not been used in a major war by industrialized nations since WW1, much of the technology may have changed. It may be in fact that they do have significant strategic value.
The chemical weapons in Syria worked. The opposition is not well trained and equipped.
And how would bombing Assad help? He is a dictator fighting for his survival and therefore has little to lose. But bombing Syria would kills Syrians, both soldiers and civilians. It would destroy people's homes (why not be empathetic and imagine your own home blown up by a bomb from Syria and the regime shrugging it off as collateral damage). It would destroy people's livelihoods (not to mention that we tend to target infrastructure such as power stations which mean people may lack electricity for months or years and even sewage systems may fail). It would wound people and inhibit their receiving appropriate medical care. It would in short inflict huge suffering.
In short people say that chemical weapons are really bad because they inflict lots of human suffering. So what is their proposed response to their use? Dropping bombs and missiles that will also inflict lots of human suffering. What then is the point?
And why if we have so much moral outrage, do 1000 deaths from chemical weapons necessitate a response, despite the fact that 100,000 deaths from conventional weapons do not?