Be slow to anger. Osteen might be bringing people to Christ and he might be misleading them horribly with unbiblical teaching. We cannot know the heart of those who come forward to alter calls, but when a teacher strays even a little from the Word (such as his belief that dying on the cross was not sufficient for salvation and it took beating the devil in hell to save us, although the Bible says that Satan is not in hell, but wandering the earth), there is just cause for concern there. If the Lord didn't use Joel Osteen he would use someone else, no big deal since each of us will presented with a chance for salvation. Christians should defend the Word and to stand up for our brothers and sisters, but we should do so in love, not in wrath.
The fallacy of "God will use someone if not this person or that person" is just that, a fallacy. It invalidates your "need" to continue living this life, and you may as well go home now. But that's not Biblical, as Jesus told us that our lives are to be abundantly fruitful. He never said, hey, if there's no fruit, don't worry, someone else will bear it.
Do you see why you hold wrong thinking?