One can be honest without being callous, harsh, or cruel. When someone says, "I'm just being honest," it translates to "I'm using honesty as an excuse to say something mean." Honest NEVER requires mean or cruel communication. Never. What needs to be said can be said in a kind way--or not at all. For the most part, qualities need to balanced; gentleness must be balanced with firmness, honesty with kindness, intelligence with compassion. As Buddha said, "Balance in all things."
Yes, it violates the "unspoken" social contract of being polite. If you see someone who's overweight, you don't go up to them and say, "You're fat." I would guess you don't do this so you still have a social filter. It makes me wonder if there's another purpose to you being harsh like you enjoy hurting people or want to drive them away. Maybe you want to see what you can get away with.
I have been accused if being brutally honest most of my life. I have found that you can still be honest and be kind at the same time. Its better to be kind while being honest. I don't mean sugar coating the truth either. Sometimes honesty is just not as important as someone's feelings. Make sure you don't confuse your beliefs and opinions with honesty. Sometimes they are not the same. By being kind I think you should never exchange honesty for dishonesty. Sometimes being honest does hurt and cannot be avoided. Just be tactful and respectful while being honest. Being honest is never wrong in my opinion but how you handle being honest can be.
I'm on board with what "koichan" said. There's nothing wrong with being brutally honest, but it depends on how you get your message across. If you're using "honesty" as a reason for acting like a superficial douche bag with the intent to hurt feelings or to degrade someone then be prepared to be surrounded by other people like you and you'll likely be accused of being lets just say insensitive for a lack of other words.
Well, sometimes. It's good to be honest, but sometimes, the truth can hurt people's feelings. For example: say a close friend of yours asks your opinion about her weight. Well, if you said "WOW! YOU'VE GOTTEN FAT!!" Then, that would hurt her feelings ( it would hurt mine... ) if you didn't want to hurt your friends feelings say "You're not fat! You're awesome!" Something like that (;
There's nothing wrong with honesty. There is something wrong with insensitivity though. Like for example, there was someone that was completely miserable towards you your entire life. Later someone that was concerned about that person told you that that person is dead. It's insensitive to go on about and say "Good" or "Ding dong the witch is dead" when that's honestly how you feel.
Also, nobody likes unsolicited advice. Feel free to be honest, but when nobody is asking you for an opinion, it's not your place to put down one.