In a commercial exchange, the party that delivers first has the right to know the identity and past history of the other party. If someone asks you to pay upfront but refuses to identify himself, you should assume he is a scammer, and not have any business with him.
You are confusing "rights" with "right to negotiate". Either side can say no for many reasons.
That someone has the right to hide his identity, of course; but, whatever his excuse, the smart option for you is to walk away.