The man in under contract. He is going to get paid near $7 million this year. SEVEN MILLION DOLLARS!!
He has an ethical obligation to uphold the contract.
That said, I do get that in the NFL this has become part of contract negotiation. Not that it should be; but it is. And the Rams know that he'll stay in shape. And the Rams will welcome him back. And so will fans.
That doesn't make it any the less unethical and wrong.