[MrScruff]

I don't buy that line of argument at all. You're claiming that if you can establish some line of cause and effect then anyone in that chain must take moral responsibility for the outcome.

That's like saying an author who writes something that offends Islamists is responsible for any violence perpetrated on them, since they had the choice of not publishing.

The moral responsibility for acts of violence lies with those that commit them, or incite others to do so.

[kstenerud]

Criminals will be criminals. They are responsible for their own actions. But if you're contributing to their coffers, you're only encouraging them. You don't even have to frame this in terms of morality. They're doing something you don't like. Do you want to help them or hinder them? Sometimes hindering them involves denying yourself. This is how boycotts work.