I remember a Wt article that addresed the matter of involvment in the job setting. For example if a JW was a customer Service person, behind a counter that had many items to sell and tobacco/lottery tickets were only a percentage of the sale., Then they could perform their duties according to a concience. If the Milk man had to make deliveries on his route that had a Drug Lord, and the other addresses were legit, then it's ok. A medical provider could reason that they are assisting in many ways, and the blood Transfusion is another product/service in the functions of the job.
Definitely, a JW wouldn't work in a Abortion Clinic.