It's not an isolated incident. If that was the case, I would understand it as we all have bad moments.
There are numerous occasions where both brothers are behaving like crazy.
Take a look at this one, where Felix lost to Duda and threw his raquet and broke a tv screen
After the incident he cries like he is a 2year old...
He wasn't disqualified just because he was playing in the doubles finals or semifinals with his brother.
At the French finals (don't remember the year) he was beaten by Alexis. Alexis was with his feet on the table and Felix was crying like a baby.
All players have been in their age and they weren't behaving like psycohpaths.
Have you ever seen Ma long, Lin Yun Ju, Kao Cheng Jui, Lin Shidong, FZD or any other player behaving like that, even at young age?
WCQ threw his raquet once and was banned from CNTT for about two months.
I mean come on, we can't justify everything on age. They are professional players, they are not 5 year olds any more...