Interesting. I was definitely too young and not exposed to their “art” to understand the reference. It’s still shocking in an age of PC and “tolerance” that engulfs Canuckistan.
Basically the punks did anything that would upset their elders who, at that point, were WWII veterans in their 50s and 60s.
Making light of the events of the Great War was a way of mocking and belittling the UK establishment.
I doubt many of them realized exactly how vile they were being.