The problem is, shareholding is now so abstracted as to make actual corrective action incredibly unlikely.

If you have investments, go and look what your holdings are. There's a real chance you have some sort managed portfolio that will trade equities to maintain growth. It might be algorithmically-driven. Your holdings may very well temporarily include some companies that you don't approve of, but trading happens so fast and so often that you're not going to be able to keep up on what you actually own.