If I mostly or completely agree or disagree with everyone in my circle, I'm probably not learning much, and I need to expand my circle (and if agree or disagree are the only two reactions I can think of, I'm reallly not learning much). And, as odd as it sounds, I'd probably learn more spending time with people I disagree with on some things than I would in circles in which I completely agree with everyone all the time.
I like... No, I love, room for doubt. I like to think things through. Wrinkles in my brain and brow are my badges of honor.
If I can simply and confidently nod my head yes or no all the time without thinking about it at least a little, it just feels wrong to me. Not because it's forced, and not simply for sake of argument or confrontation or for show. But because it gives me a better grasp of whether I'm involved in something worth thinking about.
In any case, I just prefer that everyday be an education, not just a confirmation. That's my thing.
It doesn't hold for everybody. But, at least in aggregate, everyone's life ought to have more meaning, and broader perspective, than a checklist.