i agree with your message, but your example is definitely not it. the emperor's been wanting to destroy the duke for a long time now (ever since he poisoned the duke's wife and drove a wedge between the duke and his son). it's obvious that he can't freely attack the duke, which is why he even blackmailed our MC to get dirt on him. but he doesn't need to do that anymore, not when his daughter (a literal princess, mind you) has been insulted by ppl 'lower' than her.
that reason sounds very petty but even in real life, being rude to a royalty is actually punishable

This story is forcing the characters to be more bad than they have too, like, the emperror, it's like he's charmed by his daughter, bc he's crazy with the way he twists what she says... she says the duke has more time to be with his daughter so he's gonna make him not even see her face?? Like wtf why... ┑( ̄Д  ̄)┍