I don't think it can really infect them if they didn't know about the crime until recently. That being said, I understand your concern. Christians are meant to be built different, though. Jesus was a friend of sinners. We're not assumed to be corrupted because we hung around someone who was corrupt.
The way my church's denomination does it, when a pastor steps down, they pull in a new pastor from another church, which also alleviates this concern. I say this not to defend Gateway Church (their new pastor is the old pastor's son,) but to demonstrate that not all churches have the problems you hear about.