Applying your logic, purchasing anything from US, Saudia Arabia or Russian companies is "supporting the marketplace that provides service to" government officials and politicians "of the sort that kill", abuse and torture people.
If you cast your logic-net wide enough, you can make all sorts of connections & correlations. Anything and everything indirectly funds anything and everything else.
You can't decide to shutdown all USA companies; or if you did you'd cause a lot more problems than you'd solve. But you can shutdown a website selling illegal drugs. And that would arguably solve more problems than it would cause.... arguably, maybe. I could cast the logic net even wider. The whole earth would be better off without humans probably. Do we want to have that debate? No. Humans, for better or worse, are here. The USA and its companies/corps are here and exist. That's gonna be a thing for the foreseeable future. A drug website is more reasonable to talk about if it should exist or not.
It is not reasonable to talk about the existence of black markets. They existed, they exist, they will exist. I am nearly sure that as an economic and social constructs digital black markets will outlive companies/corporations.
Also your reductio ad absurdum about humans is well, absurd.
Yes. Depending upon which candy bar I buy, I am indirectly supporting child slavery. Sadly almost nothing in our modern day society is victimless even though most pretend (or believe) otherwise.
Do you agree?