My headcanon is that factual incorrectness is their trigger. If you say you recreated something that they can factually verify was not actually recreated, just imitated, they will destroy the offending knockoff, but leave you unharmed if the effort was sincere. Basically, they don’t see this as rude because in their culture, a failed recreation brings you and/or them shame and it must be destroyed to restore honor.  
This leads us to how they deal with deceit, in this case declaring war. Taking credit for recreating their music when they only pretended to play broke one of their cultural taboos. They fix mistakes by destroying them, but liars cannot regain their honor, so they are treated as living mistakes.

THIS FANDOM NO LIKE TUMBLR FANDOM! YAK SMASH!

Rutherford: Did I just see you talk back to Yakity Yak?
 
OC: Yeah? So what if I did? Come at me bro!
 
5 seconds later in the hospital.
 
Me: You really shouldn’t give him ideas.
 
OC: Nyu shouldn’t give yihm nyideas!
 
punch the cast!
 
OC:Eee…..OOOOOOOOOOOOW!!!

pussy

“DOES YAK LOOK ANGRY!?”

Season 5: Trigger Warning season.

How dare you like something I don’t like!

I really like how Prince Rutherford looks with his mane out of his eyes.

These ponies and their cultural appropriation.