I think the utopian socialists tried this, it's been pretty well accepted for well over a century by any serious socialist thought that just talking to capitalists to convince them of anticapitalism - and this is what you're talking about when you're asking fossil fuel shareholders to act against their profit motive - simply will never work.
They will kill to protect their money. They will not listen to anything but the exercise of power. If you don't have a controlling interest in a company, you don't have power and you won't influence them. If you could get a controlling interest, you'd be coopted into the capitalist machinery long before the point you could change the fossil fuel companies' course. If by some miracle you could avoid that, I imagine you would be assassinated.
Don't kid yourself. Shareholder meetings and votes and whatever other structures create the illusion of accountability only go so far as they are useful in maintaining power for those that have it. The second you really threaten their power the fangs will come out. They will not lie down and simply agree to stop being the bourgeoisie. The apparent civility of a shadeholder meeting is a fig leaf on their blood-drenched bodies.
