Isn't the logic of fossil fuel divestment such that other investors without the same moral purity will get all the profits? Why's that good?— Marc Andreessen (@pmarca) April 26, 2016
Andreessen is of course correct that advocacy divestment, to the extent that it is effective, reduces the demand for a fossil fuel company's stock thereby creating an economic opportunity for other investors to enjoy a windfall investment benefit. If your goal, as an advocate, is to financially punish fossil fuel companies, then you have failed. More than that, you have essentially created the circumstances to subsidize those who do not share your belief system.
I think the trick to understanding this apparent paradox is to reexamine the assumed goals. If we assume that the advocates are not functionally focused on punishing fossil fuel companies but are instead more interested in virtue signalling, then their actions are much more explicable.
It's not the only possible explanation but it is a tidy one.