Well, more accurately, it says producing the hydrogen makes more pollution, not the cars themselves (which is currently true, but not scientifically hard to fix, only economically difficult)
Edit:
Also. My theory is, while it would take a big shift in production methods, (using clean, renewable energy to get hydrogen) we can start doing it right now in order to help that shift.
People make the mistake of expecting a big jump, and we simply can't do that, with the infrastructure that we have in place. But we can begin to start doing it with spare private resources (and I hope someone is already doing this). Get the ball rolling, so to speak. We just can't afford to convert fossil fuel plants into hydrogen plants, without still using fossil fuels to make them... but somebody, somewhere, should start a private venture to help get things moving using alternate methods... if we keep waiting because it seems too hard, it won't ever happen.