That’s an excellent point & one I had not considered.
If you are pissed off about being pissed on then it would depend on the specifics of the situation.
For example if someone pissed on your brand new shoe, then the level you are pissed off about it may be worse than the piss on your shoe.
But if someone pissed on your head that could indeed be worse than how pissed off you are about it unless that was a service you specifically arranged.