Wait, I remember that now. Wasn't that because Joffrey cut open a pregant cat because he's a sick twisted [censored] like that? Beating as a punishment isn't frowned upon at all. Cersei has Tommens' whipping boy beaten, and Theon talks about getting beaten for knocking over Old Nan once.
Being beaten is one thing, being beaten to death is another, especially it was clearly not as punishment but as venting machine. Cercei's unrelenting sentence to whoever offended her family led examples to Joffrey. GRRM also wanted to portrait it that way to tell the cruelty runs deep in their blood, and that he never received the kind of education to become a good king. Spoiled by his mother and abused by his father, Joffrey was a monstrous child and deserved no sympathy, but he was also far more complex than your usual spoiled brat around the corner.
Isn't it exactly the same for Theon though? Born into a much more 'ecentric' family (Balon was mad, Aeron was madder, Euron was maddest) than the Lannisters/Baratheons with a raider culture, then taken away from this family at the age of 10 to be a hostage of the Starks, thus leaving him with a massive identity crisis, being too much of a Greyjoy to be a Stark, and too much of a Stark to be a Greyjoy. Then, come then onset of the War of the Five Kings, this really comes to bite him.
Still Theon had been acting very high school. No forethought of his actions, relying on one-time wit strategy, short-sighted and timid in so many ways. That makes him a lot less believable under such situation in comparison to Joffrey.
It may be a rare occation where you live, but over here we have plenty of real life and historical examples like him it's rather unsurprising. You may find Joffrey's story rather common because that kind of family issue is predominant where you live perhaps?
I guess it just kills the confusion. Since the show can only explain so much I guess it makes sense that Cleos Frey will be Alton Lannister. Many viewers that haven't read the books wouldn't understand why a Frey is with the Lannisters.
That would even be more baffling when
Spoiler Cleos died. Brienne and Jamie's strategy might have changed?