What do you mean, “non-recourse” state? What is that?
It means if you default on your mortgage, the bank can only take the house. They can't come after your other assets.
A "non-recourse" state is one of the fifty US States that have laws on the books that limit a borrower's liability under a mortgage contract to the market value of the mortgaged property. For example, in CA, where I live, if you buy a house with a purchase money mortgage secured by the house, instead of continuing to make mortgage payments you could, in effect, opt to turn the house over to the lender as payment in full. If the current market value of the house is less than the unpaid balance on the mortgage, then the lender could not (with some exceptions) collect from you the difference (or "deficiency").
In short, the borrower would lose all equity in the house and will have lost all payments made to the lender at the time he or she turns the house over to the lender, and the lender eats the shortfall between the unpaid balance of the loan and whatever the lender can sell the house for at auction.
This is the law in force and it is by operation of law a part of every contract just as surely as if it was written in bold type on the front page of the contract itself. There is nothing unethical or immoral about either the lender or the borrower standing on the terms of an arm's-length business contract.
If a borrower is so far underwater that it no longer makes sense to keep the house, and (as is the usual case) the lender will not come to terms, then there's nothing whatever wrong with availing oneself of the terms of the loan agreement and "just walking away."