I want to delete the encrypted backup of my iPhone, apparently cannot remember the backup password, but I have full access to my phone

How do I delete the backup without completely erasing the phone?

I do NOT want to decrypt the existing backup. I want to discard it. I have full access to my phone, but I can't create a reliable backup so that I can reset it and recover it (I'm just trying to unlock my AT&T phone without losing all of my data). I do NOT want to erase all of the data on my phone. Erasing it would make no sense, since I have full, legitimate access to it. My iCloud backup does not contain all of the data that I want to retain after resetting the phone (to unlock it). Besides, restoring from iCloud won't delete the backup password anyway, will it? I'll just be stuck with the same password that I apparently can't remember. I just tried installing iTunes on a completely different PC (my new Windows laptop), logged in to my Apple account, and it immediately checked the "Encrypt iPhone Backup" checkbox. I cannot uncheck it without, apparently, the original backup password.

There are literally zero security advantages to the way this works. I am trying to DELETE the backup, not get into it, so that I can create a NEW backup of a phone I have full control of. Without full control of the phone, I wouldn't be able to create a new backup, right?

I don't believe that I'm not using the right password to decrypt my backup, anyway. I've seen this with more than one person. They try to restore their iTunes backup, using the password that they originally set on the backup, and the restore fails with a password error. I certainly haven't forgotten any of my other passwords, and I don't believe I forgot this one.

Help? What am I missing?