when is a word derogatory?

So today I was having a talk with my 16 year old niece and she says" if I put tape on my glass I will fit right in . we even have a geek day, where we dress up like geeks for fun." when I explain that dressing up like "geeks" for a fun day at school was still derogatory her response was they do it on tv so it is ok. I of course was thinking " so they shoot people on tv that's ok right?" even my sister thinks that dressing up like someone doesn't cause those who do dress that way normally to feel like outcast. ( of Course my niece's finally response, I was making a fun day at school into a bad thing. mmm I thought school was for learning ??)

The definition of derogatory is " showing a critical or disrespectful attitude." So for me a word becomes derogatory when it is used to make others feel like an outcast or to feel ashamed. in today society we are constantly trying to reclaim words and change their meaning. For our black youth it ok to call each other niggar , gays use dyke or fag, and feminist even use the word bitch . But what if you happen to find the word offensive or derogatory ? you are told to grow a thicker skin. So sorry that you have lived long enough to remember words like "niggar, fag, dyke" being followed by a beating or being arrested.

And of course we got media telling us it is funny to single out a person(or a group of people) for anything we find different in them.  When we consider ourselves so enlightened and tolerant of each others feelings, isn't it funny we still  have a society building on putting others down?  Now we have convinced ourselves that if we are the one putting ourselves down it doesn't matter???

what happened to teaching our youth respect?? we don't even teach them to respect themselves and we wonder why so many of them turn to drugs?? Why so many become depressed adults ?? I watched a great video recently that i felt really ties in with this. (http://www.upworthy.com/one-of-my-favorite-authors-says-theres-something-we-should-remove-from-all-classrooms?g=2&c=ufb1) the old saying stick and stone will broke my bones but words can't hurt me was so wrong. Words cut deeper than any other tools.

thoughts? opinions??