I'd love to think that "truthful and honest" would work, but it seems pretty unlikely to me. If it's going to cost anybody money, or even just face, it's going to be pretty easy to instill fear, uncertainty, and doubt. As you say, the Koch Brothers are winning, but I can't think of any way to prevent them from winning. The deck is heavily stacked in their favor.
As scientists, we like to think that the universe ultimately and undeniably stacks the deck in favor of reality, and that's true... eventually. A century from now, people will look back and say, "Wow, the data was all there, and it was really obvious. It would have saved so much pain for them to make small changes back then." But that's retrospective. All but the very youngest of denialists will be safely dead before they're forced to confront reality. Even then, there will be those who will blame Milankovich cycles or volcanoes or even just say "look at all the wonderful new Canadian farmland we have!"
So honestly... I really don't know what "truthful and honest" will get us. Sure, hysteria will turn some off... and it will click with others in a "Won't somebody think of the children!" kind of way. This is persuasion, not science, and I truly can't tell you what the most effective tack will be. But there has been plenty of clear-eyed, non-hysterical discussion available for decades, and polls show that it's losing. You can blame the more aggressive promoters for that, but I think that's just an excuse. Really, I think that people will mostly continue to believe what they want to believe, especially when the Koch Brothers and the Daily Fail give them all the FUD they can swallow, and even if there were not a single overhyped story it would have been precisely the same. It might even have been worse.