> Very intelligent, otherwise rational people believe in false propositions that make them feel happy, relieved or secure all the time.
Exactly. I too have found that many people like to have their "ears tickled". It feels like people don't want to put up with sound reason and instead believe in doctrines and beliefs that suit their own personal tastes.
>An afterlife doesn't need to be proven false. There just has to be some evidence,
Very true, many belief systems over the millenia have taught an afterlife scenario (commonly following a 'Good Afterlife' vs. 'Bad Afterlife' theme). This comes from many belief systems carrying the notion of a "part" of the human that carries on immortally beyond the physical body (believed to be an immortal soul by Christian groups -- interestingly, the bible carries no support of this notion).
Even people who believe in this immortality notion cannot provide evidence of it's existence, yet work on the assumption that it can't be proven false. (Although, depending on your authoritative scriptures, it sometimes can be.)
A political Jewish group in the days of Jesus were known for strongly believing in the Torah, but not in this immortality notion [0].
[0] http://en.wikipedia.org/wiki/Sadducees#General
>You're made of meat, death is final, there is no do-over.
I agree. Humans cannot stop death on their own, if they were to ever have a hope of overcoming death it would have to be via some external force that was vastly more powerful and smarter than they. Many ancient belief systems attribute this power to either a God, multiple gods working in unison, or to 'The Universe' (as in: that is simply the ways thing are).
In summation, it's NOT okay to say: GOD EXISTS! or GOD DOES NOT EXIST! or whatever oversimplified nonsense you can angrily yell in under 5 seconds and proceed to use as the foundation of the ideals for your entire life.
A truly rational person understands this.