Our ancestors engaged in a war against death that we're still fighting today. They threw everything they had and everything they could think up at the enemy, and as a result we now have science and medicine and religion and, really, the whole of human culture. They were relentless and tenacious fighters, but (being rational creatures) they understood the limitations of the war they were able to wage. As a group, the clan/tribe/people would fight on until the end of time, making what progress they could against death. But as individuals, it had to be acknowledged that each and every soldier would one day fall to the enemy.
That was a terrible thing. An unacceptable thing. But it had to be accepted anyway. Refusing to acknowledge the inevitability of death would have made as much sense as refusing to acknowledge the inevitability of gravity. It was pointless, and you would go crazy if you thought too much about that kind of thing.
unfortunately, I think the only way we'll get to the point where people no longer "know" that death from aging is inevitable is when we have some very youthful 80-120 year olds who can attest to it personally. Yes, a lot of people will needlessly die between now and then. But again, we're talking about an unprecedented paradigm shift. Once we cross that particular chasm, my guess is that things will happen very fast. The rage that Jay is looking for will be awakened, and it will completely reshape our world.
You might recall that Phil has an article at the Longevity Meme that gives a good overview of his thoughts on the topic of aging and death. Personally, I think we can do better than Phil's guess at the future in that last paragraph above - the very existence of the anti-aging industry shows that people are very forward-looking and anticipatory in this matter.