Most have erred in some way, the question is whether the error is critical or not.
If a pastor struggles with a sin issue that's one thing. If a pastor promotes a teaching that fundamentally misses the mark regarding the person of Jesus Christ that's pretty serious, no? If Jesus Christ is our foundation and we've got something fundamentally wrong regarding who Jesus Christ is and was, anything we build on that is also going to be suspect. It comes back to the parable about the man who built his house on the sand. A false Jesus represents a foundation of sand, and when the storms of life come the house built on the sand won't last.