There's a difference between teasing, and bullying.
If someone called you a *****, or a sissy. (Whatever insult) you really should just shrug it off, but the thing is that's no longer the problem. Bullying has become much more than just teasing someone, and sometimes it results in physical violence. That's the issue here.
I was bullied ever since grade school. The kids pushed me into the mud, and I had to call my parents for another pair of clothes. Is that acceptable? Should I suck it up, and deal with being pushed into the mud? The answer is No.
I was basically shunned in all my schools for being different.
When in middle school I got my first girlfriend, and people were harassing her. "Ew, why would you go out with him?!" and, they were telling her made up stories about me, and trying to ruin my relationship with her. Is that acceptable? Now you're just going out of your way to ruin someones love life. Is that acceptable? Lucky for me, she stood up for me, because took the time to know me.
I suffer from severe depression. (It runs in the family, something I can't help) Between that, and getting bullied at school to the point I skipped school for 4 months towards the end of the year, because I had literally no friends left. Due to me standing up for myself, and socking some freshman in the face for making fun of me first thing in the morning, and yet I am the bad guy? Ha. Nice friends I had. They are turned their backs on, and made fun of me as well.
So the entire school was against me, and made not want to go to school. I was A student, but the constant bullying made me left. I couldn't even open my mouth in class without people insulting me. The school doesn't care, and my father was emotional abusive towards me. So between school, and my home. I didn't have any where to go.
So yay for me.
I can see your point, and in some ways I agree with the OP. Kids should just really shrug off the name calling, but it isn't just name calling anymore. Some kids are going out of the way just to hurt you, and make fun of you. Bullying has become a bigger issue due to people becoming more desensitized. That's why it's a big problem in our country now, because it has become so much worse than just teasing someone.
Like I said above they want as so far as to harass my girlfriend at the time not just in school, but also on facebook. Saying things like. "How could you ever date that freak? He's so ugly!" and crap. They pushed in the mud during grade school, and tried to beat me up. (Tried but never won.

I was strong as a kid, but over the years the depression made me not want to exercise anymore)
So it's just not name calling anymore it's turning into harassment.
I can see your point, and some degree I agree with you, but when it turns into harassment that's where the line should be drawn. Bullying is part of life, and it should be. It teaches you to stand up for yourself, and teaches you that people are going to make fun of you where ever you go in life. That not everyone is going to be your friend, and hold your hand. This I agree with, but it's turning into harassment now, and not just "teasing"