Similar thought: should you have a moral quandry about doing work for a car company, given that 1.25 million people per year are killed in road traffic incidents.
This takes you down a never-ending and unproductive rabbit hole. We really aren't equipped to encompass the totality of the effects of any particular action we take, which will invariably, at some point in the chain of consequences, have adverse impacts on someone, somewhere.
It depends. If the people are dying because the cars we make have break pads that haven't been certified as safe, and the reason they aren't certified is my boss said to not do it coz certification raises our costs by $1000 per car, yeah, I'd be bothered. Big as they come moral quandary.
I'd focus on the difference you're making. Are you making drivers, passengers and bystanders more or less safe than they'd be if someone less skilled was doing your job? Given that new cars tend to be substantially safer all round than older cars, I'd say most of the industry is in the clear. OTOH anyone encouraging people to buy heavier cars than they need should probably think things through pretty carefully.