> But when you get drugs from the drug cartel, the harm that goes into the production makes it wrong to use.

That doesn't really follow. Nazi medical experiments were wholely unethical, but it would be completely unethical not use whatever knowledge they gained to save other people's lives.

Perhaps what you meant to say is that it would be wrong to pay for the drugs so the cartels actually benefit from their unethical behaviour. I agree with that, but that doesn't make the drugs unethical to use.