You are misunderstanding. The question was why the BND sharing with the NSA was worse than what the BND does on its own.
What I was saying in response was not there is perfect safety against abuse, but that if the BND could share information freely with the NSA, it would render the existing safeguards largely worthless, because the NSA is not bound by the national laws of Germany.
What I was saying in response was not there is perfect safety against abuse, but that if the BND could share information freely with the NSA, it would render the existing safeguards largely worthless, because the NSA is not bound by the national laws of Germany.