Some members choose to remain anonymous when viewing profiles. These members do not choose to be anonymous when only viewing certain profiles. Instead, they choose to be anonymous when viewing all profiles. You can't block them or force them to reveal their names in order to view your profile.
When free members choose to remain anonymous, they won't be able to see who's viewed their profile either. If you have a Premium account, you can browse anonymously and still see the list of people who viewed your profile. However, even if you have a Premium account, you still can't view the names of anonymous viewers of your own profile.