The problem with "brutal honesty" is that some people enjoy the "brutal" part more than the "honest part. The question to ask yourself when confronted with a rude person who claims their rudeness is really just them being blunt or honest, is to question their motivation first.

1. Is their feedback factually correct? Or just their rude opinion?
2. Is their goal to hurt your feelings, or to protect your feelings?

The brutually honest person may claim they observe something about your appearance or situation that you are oblivious to. But you need to discern for yourself if they have your best intentions at heart, or, if they're just being a jerk because they know how to push your buttons and manipulate you emotionally.

True friends have the ability to be directly honest with you, because they have your best interests at heart. They want you to improve and grow.

If you can't be honest with yourself, then anyone's criticism or observations of you will put you on the defensive. But, once you are confident in yourself and don't care what other people say about you behind your back (or to your face), then other people's criticisms won't bother you.

Oscar Wilde said, "true friends stab you in the front." True friends can walk into your dorm room and bluntly tell you, "wow your dorm room stinks! how long's it been since you did laundry?" Then they will laugh or tease you about it. But my point is, you already know they mean you no harm because there's established trust and respect already between you two. But if an acquaintance or stranger makes the same comment, and you feel embarrassed or insecure, then of course you'll be on the defensive.

Brutal honesty is a process - it's neither good nor bad. But rude is just plain rude. There's a huge difference. Hope that helps.