From Dead Air by Iain Banks:

'I believe in truth,' I told her. She was smiling a little now. I was making a complete idiot of myself but I didn't care any more. 'There; I said it. I believe there is something pretty damn close to objective truth more or less all the time and I'm not accepting this shite about everybody having their own truths or respecting somebody else's opinions just because they're sincerely held. The Nazis sincerely hated the Jews; they weren't just kidding. I'm not respecting their fucking ideas just because they were deeply held. I believe in science, in the scientific method, in doubt, in questioning, in facing truths, not hiding from them. I don't believe in God but I admit I could be wrong. I don't believe in faith at all because faith is belief without reason, and reason is the only thing we have, the only thing I do believe in. I think people have every right to believe in anything they want, no matter how ridiculous it might be, but I don't accept their right to coerce others into the same views. And I certainly don't accept any right they might think they have not to have their views challenged just because they're going to feel peeved in the process.