This clearly shows the lack of understanding how Monero works. I'll assume it's just an IQ problem, if not you're just FUDding.

Monero transactions can be proved by both the sender and the receiver.

When the receiver claims that he did not receive the money, 2 things can happen.
1) either the receiver discloses his viewkey. This will result in everybody being able to check if the money did arrive or not.
2) the receiver doesn't want to disclose his viewkey for privacy reasons, and asks for the sender to disclose the transaction private key. This key can prove an outgoing payment from a certain address on a transaction per transaction basis. The sender won't lose privacy when he does this, except for this one transaction.

So the quoted statement is BS.