I am surely not an expert on the field, but I heard some people say that NIST P-256 somehow has backdoors.
I don't know about the seriousness of this claim; maybe it's just a conspiracy theory.

If there is some truth in that it, why is NIST P-256 still implemented? Almost everyone I asked said it's a bad idea to use P-256. If this is true:

1. Why is it still in GPG (as of 2017)?
2. Does it have any use (expect legacy and compatibility)?
3. Is it really broken to the point to be unsafe to be used, in a professional environment?