Well at first I thought it was Kate who was complaining about going to Human Rights Court but now I see its William.
He's never tried to make any public impression on the press and he's had a difficult and sometimes antagonistic relationship with the media before he met Kate so I guess he's still gun-shy from his mother's experiences.
In that case, it doesn't matter what Kate thinks, William's knee-jerk reaction will always be to shield himself and the ones he loves. It may not always be the wisest decision but I think its the right decision here.
As I said before, being in a public position, they need to set boundaries with the press or the press will walk all over them. Now if he were fighting with a reporter like Harry did, I'd say he's gone too far. Far more civilized just to take the scumbags to court.