It didn't act unethically as a business partner. It withdrew from being a business partner when it found extremely bad behavior and then, rather unsurprisingly

It didn't act unethically as a business partner. It withdrew from being a business partner when it found extremely bad behavior and then, rather unsurprisingly given that it is a newspaper, it published it. Even if your business partner is not a newspaper, if you show them something highly unethical in secret, it is not unethical for them to end the partnership by passing on what they know, whether publicly, or to regulators, or to the police.