There's no way you can prove any of this stuff. People have experiences that lead them to think one way or the other. As someone who used to get very self-righteous about debunking anything spritual or "otherworldy" myself, I can relate. At some point I stopped caring why other people thought what they did. Don't see the point. If someone has something that gives meaning to them, where is the threat in that to you personally?
There's people on this site like myself who now do believe there is more than meets the eye in life. Everyone has the right to bash or make fun of someone else's beliefs, but from my experience, the ones that do that, have some baggage regarding the topic. There's a reason they can't stop trying to tear it down, because they haven't made peace with themselves regarding whatever topic it is. Otherwise they wouldn't even bother.
At least in my case, that's how it was when I was overly active on atheist message boards, spending countless hours debating believers and doing my best to prove them wrong. I had unresolved issues. Once I KNEW, without a doubt, that I was RIGHT, I stopped caring about their beliefs. Their belief lost all the power it had over me, and my need to debate about it, basically stopped.
By doing that, I was more free to be open minded and create my own belief system. And by doing that I was less threatened by others. Not saying I don't still like a good debate, but it doesn't matter to me as much, or at least, not for the same reasons.
BTW I have bought two books from Tolle, And I've read the Power of Now about three times so far. It has helped me be more relaxed, given me a healthier perspective, and I am much happier. And no money was taken from me, I paid gladly. I may give it away to someone, and buy another one. It's only money.