Whether it has been altered or forged is another story. The point is, demanding some other record because that kind of certificate isn't good enough, is false. It is good enough.
Good enough to establish the facts that it contains, nothing more. Not necessarily good enough to determine natural born citizenship.
Also when a forgery is suspected or alleged, the "source document" is a good place to look to corroborate the facts on the derived document.
But you were insisting that it was a "source document", that is copy of an "original birth record". It's not. I'm glad to see you finally understand that point.