I might be wrong. So what?
I might be wrong about anything I think is the truth. Under the scientific method, you can be absolutely convinced only that you're mistaken; you can't ever be absolutely convinced you're correct about any specific proposition. I might be delusional. Any of my experiences, experiences that I'm convinced are reliable and veridical, might simply be deranged fantasies. I could be wrong that I'm a rational person. I might think I'm a rational person, but if I'm not rational, if I can't use logic effectively, I would still think I was rational. I could even be wrong that rationality itself is reliable and veridical.
All of my moral and ethical beliefs, my evolved and socialized judgments, might be completely wrong. The war in Iraq, a patently aggressive war of imperialist conquest, might be the right way to conduct international affairs. Slavery could be the key to a perfect society. Rape might be the best way to have sex. Women might be nothing more than walking uteri, for whom lobotomy would probably be a kindness. Torture might not only be acceptable, but should be routine, perhaps even to extract confessions for traffic violations; it might even be that we should consider a confession reliable only extracted under torture. Perhaps the world of 1984 is a Utopia, not a dystopia.
The ancient Greeks went down this road a couple millennia ago, and from them we have the root of Big-ess Skepticism: We don't know anything, and if you're not perfectly certain — and you can't be perfectly certain — you have no ethical or epistemic warrant to do anything but shrug your shoulders and say, "I dunno." This nihilism applies to everyone: the religious can no more be certain they are choosing the right scripture, or interpreting it correctly than can the rational scientist or philosopher be certain that rationality is reliable.
"The best lack all conviction, while the worst / Are full of passionate intensity." Yeats is not expressing a norm here, he is making a complaint.
Nobody ever takes this sort of Skepticism to its logical conclusion of total ethical and epistemic nihilism and paralysis. It is always those who disagree who lack the warrant to draw conclusions.
So I don't put on an air of faux tolerance. To be tolerant just because I'm uncertain is to tolerate not just different opinions, but everything: stupidity, lies, rape, murder, torture, slavery, genocide, wars of aggression and conquest, and mopery on the high seas. I have beliefs, I've drawn conclusions, I approve of some things and abhor others. If it sounds stupid to me, I'll call it stupid. If it shocks my conscience, I'll howl with outrage.
I do the best I can with what I have, If I'm wrong, so what? I'm wrong. Not the end of the world.