Tools don't kill. It's the ones wielding the tools that do.

A black home bomb is harmless until someone uses it to wipe out an entire solar system.

I don't work for them because I chose not to, but honestly, work for them, don't work for them, it's not like they'll lack for employees. If you write that line of code that eventually blows up a hospital or someone else does, it will still happen. You're not going to stop them by turning down job offers. You're going to need to change politics.

Hey!  Thanks bro. I'll be nice and cool by my pond. Im Canadian and I was working for a US defence contractor. I was in their industrial sector and worked in Europe, never touched a defence product and wouldn't be allowed to. But every time the quarterly numbers came out and number went up. I couldn't help but feel responsible for steering them profits. 

I'm unemployed and the happiest I've ever been

I'll be honest, I'd rather the best engineers be there to create weapons that are extremely precise. The weapons are gonna be made regardless, but I've seen photos of what happens to cities when bombers are dropping unguided munitions. Back during WW2, if you wanted to hit a factory in London, you didn't just drop 1-2 bombs, you dropped hundreds of bombs, you flattened absolutely everything in the area because that was the only way you were gonna hit your target.

At least with precision munitions, if you're doing war 'nicely', you only hit what you intend to hit, not your target + everything else even remotely close to said target. With precision munitions, you can't 'accidentally' bomb a hospital, so when you inevitably do bomb a hospital, you don't get to go "Oh oops no it's not my fault it's the bombs' fault!". The sights are crystal clear, the plane/drone moves exactly where you want it to, there's nothing interfering with the guidance, the bomb locked onto the target you wanted to hit, and you dropped it, all thanks to engineers making those systems. You had everything going for you as a bomber to know exactly what that target was, and you dropped the bomb anyway.