I'm not saying it's disrespecting the family name, I'm saying it's disrespecting his father specifically, and that's fine.
I think the religious opinion analogy is slightly different, this is someone who:
- Has a name that has an association to another person.
- They don't like the other person.
- They want to change the name to remove the association.
That is a valid thing to do, but it is directly disrespectful to the other person because it directly expresses the fact that they don't like them.
It is fine to not respect people based on their choices and behaviour. It is fine to express disrespect to people you don't respect.