I really hope the OP has a long list of these attack posts, because they are so amusing, but just in case not, here are some ideas:
William refuses to wear a wig in a deliberate snub to British wig makers
Catherine has persisted in spelling her name with a C, implying disdain for those whose names begin with a K
William deliberately outgrew his father and brother with no thought to the trauma this might cause them
Catherine smiles too much, mocking those who cannot afford a dentist (don’t try ‘their smiles frighten me’ though - been done)
They both wear leather shoes with no thought for the environment / they both wear vegan shoes with no thought for the environment (take your pick or maybe alternate?)
William has a friend who is Jordanian (oh sorry, think this one has been done, but you could add something about converting to Islam?)
Catherine looks too good in clothes, in a clear snub to anyone shorter and fatter than her
Catherine’s hobbies include playing the piano, drawing, photography and going to exhibitions, which is clear evidence of no interest in the arts and being obsessed with tennis (sorry, another one already done but maybe something about inappropriate friendship with Roger Federer? He is Swiss after all and has two sets of twins which is just plain weird)
William refuses to profit from his mother’s story, solely in order to make those who do look bad
They never talk about security concerns which just goes to show that there aren’t any, and that’s because they are so unpopular and irrelevant
Catherine is a nonentity (done recently but not very well - could retry?)
William supports a football team that plays in the same league as Man City and yet has said NOTHING about the cheating scandal
They have at least one dog but never show any interest in cats - deliberately alienating a large section of society
William persists in being left handed which we all know is very dodgy, especially when Sophie is also left handed but HIS OWN WIFE isn’t.
Catherine cheated in the Three Peaks Challenge because she didn’t ignore all the advice and do the driving herself (sorry - been done, but could say it was only to make people who do piddling little hikes in California feel inadequate?)
etc etc etc