The Christian Inquisition

I've often wondered what degree of examination is appropriate when it comes to the faith/beliefs/walk(Christianese) of both myself and others. Essentially, how right do you have to be to be saved? This is a complex subject, and I'm not going to get into it right now for two reasons. 1. I don't know very much. 2. see first reason. Here is what I think is true. American Christians (I don't know much about international Christians, either they keep to themselves or I am purposefully oblivious) seem to love to pass judgment on other Christians. Very quickly, the question of "is it wise?" becomes "are they even Christians?". If you don't think that is true of you (I already know it is true of me) than consider this: when was the last time that there was a Christian with whom you fundamentally disagreed of whom you thought "Thank God for the work He is doing through them"?. Here is an example: Joel Osteen. I don't even know if I spelled his name correctly, but that is beside the point. Osteen seems, from my perspective, to be enamored with the prosperity gospel. I think this is a huge aberration from the point of Scripture and, ultimately, the point of the gospel. I think that oftentimes Osteen preaches everything BUT the gospel. However, I am confronted with this reality: Scripture says that anyone who believes in the person and work of Jesus Christ will be saved. If Osteen believes that truth, he is undeniably a Christian. That makes me upset, but that doesn't matter. I might spend the rest of my life thinking he is deluded, that he is leading people astray, etc, but it doesn't change the fact that Osteen is a Christian. I don't know Osteen. I don't know his motives and I don't know his heart. It is true that Paul says that teachers are judged more harshly than others, but it is also true that Scripture is firmly rooted in the reality that whosoever believes in Christ shall be saved. I know, you're thinking "but Scripture says you will know them by their fruit". That's true, and that's the reason that I wrestle with this so much. As Christians, we love making decisions about the state of other so-called believers' souls(There was a time in my church where most people weren't even sure if Donald Milller was a Christian(I was one of them)). I know that we can discern good doctrine from bad doctrine, but can we know the state of another's soul? What is the difference between someone missing the point of the gospel and purposefully misrepresenting it? Is Osteen deluded or malicious? I don't know. What I do know is that I don't accept his teaching, but I also know that the qualifications for salvation are simple and straightforward. C.S. Lewis once said that when we get to heaven, we will see that there are two kinds of Christians: those who were wrong and those who were very wrong. How does the balance of knowing people by their fruit fit into those dichotomy? Are you(am I) in love with passing judgement on other Christians because it makes us feel better, or do we do it out of a love for truth? I think it is both. Christians(myself included) are eternally suspicious of one another. I want to love doctrine, but I also want to love others, especially my brothers amd sisters in Christ. What is the right balance?