I feel like you're misunderstanding a few things.
The easiest way to explain No Guard is that it turns all attacks into Aerial Ace, i.e moves that don't check accuracy.
Protect does not have accuracy. It doesn't target itself, it simply happens. It has no targetting and no accuracy.
No Guard affects attacks with an accuracy check and then ignores it. Protect does not have an accuracy check, so it wouldn't be affected by No Guard at all.
Category Status Status
PP 10 (max. 16)
Makes contact? No
Introduced Generation 2
No accuracy, no relation to No Guard.
I understand it says 'accuracy' in the description but that isn't really (ironically) accurate. Showdown for example also describes it as failing, and literally all of its ingame descriptions say 'fail' rather than 'miss'.