If it serves no purpose then it is the opposite of reasonable. It is unreasonable. It is unjustified.Apology accepted.You don't understand the meaning of justified. It has to do with justice, not empathy.When I say "justified", I mean that I understand why they feel that.
It does not serve a purpose, but I understand why they would feel that.
Does that make it clearer?
Justify
transitive verb
to prove or show to be just, right, or reasonable
I was using it in the "reasonable" sense, not the "just" sense. But I apologize for confusing you.
How can hating Hitler be reasonable and serve no purpose?
I don't understand why you can't see the answer to your question.
The fact that it is reasonable to expect someone whose family has been killed to hate the man behind it is unrelated to whether or not that hatred serves an external purpose.
It serves an internal purpose. It makes one feel better, in a roundabout way.
It serves no external purpose. In fact, hatred can only make you act worse - it can never make you act better.