Yes, gifts are legal. But the attorneys weren't asking for a gift, they were asking him to sign a binding legal document. And generally the law does not recognize "gifts" to for-profit entities; such a transaction is characterized as a contribution to the entity...which in the original comment would have defeated the very purpose of the agreement the attorneys were asking him to sign.

Furthermore, consideration isn't required to enforce future performance. It's a fundamental basic requirement to have a contract in the first place. Without consideration, there is no contract.