I would suggest contacting Sony concerning recovering your PSN account. This will save you a lot of trouble and let you keep your current Bungie.net profile. If you are unable to gain access to your PSN account, then you will not be able to unlink it from your current Bungie.net profile. If you're trying to set up cross-save, then your only option will be to create a new Bungie.net profile and then unlink/relink the accounts you actually want to that new Bungie.net profile. The reason it's a thing is because it's a security measure to insure that someone who might log in with one of your accounts cannot take over your Bungie.net profile and kick your accounts off of it while adding their own, completely claiming ownership over your Bungie.net profile and whatever goodies you might have attached to it.