There is no type of war that should be considered good, not one. Chemical warfare is probably one of the worst types of warfare that exists today. Using chemicals on poor people who do not deserve it is uncalled for and sick. I do not see how anyone could do that or order someone to do that to another human being.
Chemical warfare is generally not at all a good thing. There's a reason why it's been banned in almost every rule of warfare ever made. Chemical warfare might be a cheap and effective way of killing thousands, but the way in which those people die is horrific and should not be condoned under any circumstance.