Seems there's two viewpoints here.

The first is that the OP purchased a CE ticket and should be entitled to the CE benefits offered, despite deliberately disobeying the CC's polite request to pay attention to a 5-minute safety briefing at the start of a multi-hour (I assume, the OP didn't specify where in Germany they were returning from) flight.

The attitude that as a status passenger travelling in CE, you can pretty much do what you like and the CC are there to provide a product is the same kind of elitist, arrogant behaviour that we lambast and make an example of in the DYKWIA thread.

The second view is the one undoubtedly taken by the FA in question, which is that as a passenger on board a BA aircraft, you are required by BA policy to pay attention to the safety briefing when it is given. Granted that most passengers tend to zone out (I personally casually glance out of the window during push-back) but having headphones on and blatantly ignoring the briefing is just plain rude.

The reaction of the FA is, granted, a smidge on the childish side, but totally understandable and I'm sure some FAs would have said a lot worse than a polite retort. No doubt CR will smooth things over with magic words and bung the OP a few Avios for his "troubles" but if I was the FA, I'd have done exactly the same - and I wouldn't have been as polite about it either!