Why Can't We Both Be Wrong?

This is a continuation of pots and kettles, except this has a different thrust. Basically, if you're not perfect, you can't criticize people, and if you criticize people, you must think you're perfect.

So why can't we both be imperfect? Why can't I say "Hey, those Israelis sure treat Palestinians poorly, and those Palestinians sure do bad things to Israelis." Why can't both of those things be wrong (in this case, I don't mean factually, I mean morally)? Why can't I decry both? Why do I have to approve of Israel's policy because some Palestinians are terrorists (and don't get me started on the fact that I have to approve of Israel's policy because of the Holocaust). Why must Israel be wiped off the map because it treats some people badly?

It's really just another case of there being no room for anything but extremes. In political parties, you're either with everything or agin' everything, and ne'er the twain shall meet. So obviously there's no way for you to be wrong at the same time as your opponent is wrong. There are only two things which can happen: I'm right, or you're right.

Likewise, why can't we both be right? Religions seem to take a dim view of that, historically, as do various other people and organizations, but why can't we both be right? And not in the partial sense; there are some things where both sides can be entirely right. They tend to be metaphysical, but still. I don't mean agreeing to disagree; I mean agreeing that we're equally right.

I'm hearing strains of "Why Can't We Be Friends" running through my head, and basically this was just one long question of that sort. And yet, I ask: why can't we both be wrong? Why can't I admit that I'm wrong without having to agree that you're right. Why can't I be right without you being wrong? What the Hell is wrong with us?