Good luck getting a vote at Aramco or PDVSA or anything in Russia. They'll be laughed out of the room if they're lucky and probably murdered if they get too annoying.
Either way Exxon totally has a way to reduce the emissions of their customers: by reducing their customers. They may go to other producers but this is hardly the only thing activists are trying. It's not an impossible request and could be a useful component of a larger strategy.