My preferred answer was quite simply to tell the truth. To me, the truth is pretty much it. If you have to lie to convince people of something, then that something likely isn't of value. Moreover, once the lie is discovered, people will naturally gravitate towards the idea that your idea is incorrect anyway, regardless of its actual merits.
For example, look at all the scandals coming out involving green energy and climate change. Even if you believe in such things, all the stuff with Solyndra, Climategate and all the rest are only going to hurt your case. I can easily say the same for people who fake miracles, the guy who put an orangutan jaw on a human skull to claim evolution was real, and all the rest.
Whether you shift the truth or simply obscure it by destroying evidence, either will only cause problems to surface later. This is part of why I believe history repeats itself; people make the same mistakes until they understand why they did something, and can then learn from it.
I have many comments about the game and the endings, but as requested, won't list them here.