I'll say it like this, there's nothing wrong with rating them, after all your rating her is just your PERCEPTION of her, particularly from a physical standpoint.
The problem that guys typically have is they let their perception of the chick CONTROL how they act around her. They get dopey, sappy, and let her get by with bullshyt that they would not normally let anyone else bet by with. Or it could be the to the other extreme where they may treat her like a complete outcast when she might be an otherwise nice person.
Or it can make the guy feel insecure about himself.
So as far as I'm concerned, there's no problem in rating chicks.