I make and sell soap. The soap contains an ingredient that anyone can use to make bombs. Some people buy my soap only for that purpose. I know because they literally tell me how they use my soap. I can remove that ingredient but I would loose a lot of sales.

The police finds my soap in the lab of someone who blew up a building. Some people died. Was it my fault, knowing how it was being used? Did I do anything illegal? Unethical? Immoral?

Interesting thought experiment, but no, I don't think it's llegal/unethical/immoral to sell that soap. But in practice this sort of business will change their formula to avoid bad press and regulation.

Having done some internet things (email stuff) that have been abused by others I always felt obligated to make the abuse as hard as possible once I found out about it.

I am not sure about the legal standpoint, but from a moral one I would have felt bad running the business knowing it's regularly abused to harm others and I am not doing anything against it.

Jail is for people that don't accept constraints outlined by democratic society.

This is a nonsense argument.

The manhattan project was very intentionally an attempt to create a WMD, it wasn’t a side-effect of something else. You don’t have a point here.

If you set up what is clearly a perfect marketplace for drugs, and you know it's going to fill up with drug dealers, and it does fill up with drug dealers, and there's one goofball that decided to sell a hamburger.... you're not an innocent guy who is running a hamburger marketplace.

It’s not not the same thing either.

The purpose of eBay isn’t to facilitate illicit transactions, doing so is abusing the platform.

SR was very much for illicit transactions.