I'm having serious issues linking and unlinking accounts. I have had an Xbox account with a number of Halo games linked to it for years. I recently pre-ordered Destiny on PS4, and went on this new Bungie site to register my code. I logged in with my PSN account, but this created me a new profile rather than linking to my old Xbox account. For some reason, I now cannot unlink my PSN account to link it to my old Xbox profile. If I log in with my Xbox profile and try to link my PSN account, it tells me I have to unlink it. Fine, so I log in with my PSN account and click unlink in account settings, and I'm told "You cannot unlink an account that you are currently signed into." This system is ridiculous! I can't unlink the account because it's signed in, but the only way I can get to the unlink link is to log in with that account! Someone please help. I'm going bananas here.
I believe that in order to unlink an account, you need to link something else to that bungie.net profile. So you probably need to log in to the account that's linked with PSN, then link your facebook or google account to it, THEN you should be able to link your PSN account from the other profile.