B) By that logic, isn't all money tainted? And everyone of us? And every thing?
This is the starting point of every person's decisions regarding being ethical.
How far back do you need to "follow the money" before you consider it "ethical"?
That is up to every person. Theil has actively engaged in dubious ethics, I won't belabor them again. With him it is one hop to "dubious", compared to other organizations where you have to make several graph node hops to get to something dubius. This is a personal choice and everyone has to do their own research if they care about it.