I was really busy yesterday when I was in this thread and just didn't have the time to post a long response to this but now I have the time and I think it's important because you bring up a couple of issues which I think cut right to the heart of the matter.
The idea that the teacher should have strong knowledge and appreciation for the material, in this case the Bible. Who is likely to have that knowledge and appreciation of the Bible? A Christian. Can that person teach that class without any bias? I don't think so, maybe some teachers could but if they can't then that's a violation of the establishment clause. This class is part of the curriculum so it really shouldn't matter who teaches the course anyway, there should be a syllabus to follow but then that brings up another problem, if you get someone who is biased against the Bible or Christianity then you're still in violation of the law.
Demand. This isn't a local issue it's a Constitutional issue. What the parents want doesn't matter if what they want is against the law. I'd have no problem with this if it were a club that meets after school even if school staff were involved, in that case I'd be all for a Christian leading that club but that's not what this is even though that's clearly the best way to handle this. Once this was made a class and is being held during the school day even if you're for it you have to admit that Proselytizing is a legitimate concern here in fact I'd say it's likely to occur. How many people do you know who are neutral on the subject of religion or the Bible?