Is 2 Kings 2:20- end the thing where Elisha called the bears to kill the youths? If so, there are a few important things to consider here. First of all, the "Youths" were not children. The Hebrew word indicates a teenager or young adult, possibly even in their 20s. Second of all, it was showing contempt for someone they knew was God's prophet. There were no "Christians" and "Non-Christians" back then, if you wanted to live in the Holy Land, you believed in God. That was the Law. God never demands that to be the Law in any other nation, but he did in Israel. It was kind of like blasphemy. Not that such a penalty, or any penalty, would be justified by secular authority, but this was by God's hand, and it was showing contempt, not unbelief.
As for the miracles thing, yes I know, but my point was, even to a non-believer, the Bible is a basically accurate historical document (Though with some errors), but not "Filled to the brim with errors."