I am a little bit confused. You singled out this girl for having such a foolish attitude towards the mentally disabled- but then, in your third sentence (not including the quote), you said "retard insulter." ? This causes confusion in me. The term "retard" is also a disparaging term. You were aware of this, correct?
This individual of whom you speak may be a troll. She may be just a big jokester. Or she may have been confessing the truth, in which case she is transparently immature. I mean, this girl has some issues. Laughing at the mentally disabled? That is pretty screwed up. Where is the sense of compassion and tolerance? If she really meant what she said, it pisses me off.
I take this personally, because I have a mental disability, myself. Perhaps it doesn't make itself too apparent in my writing, but you should never assume negative things about people. I have a high I.Q., but I have severe obsessive/compulsive disorder, and it does indeed affect my functionality. It is not a joke. It is not something to be laughed at. We should never laugh at people who may have disabilities- ESPECIALLY when they are disabled, for whatever reason, due to no fault of their own.
I am in college to become a teacher. In one of my classes, there is this young lady there who is wheelchair bound. I do feel compassion for her, but I just remain respectful towards her, and treat her just as I would anyone else. I am respectful towards her. I don't feel "sorry" for her- I just have compassion for her plight. She is not beneath me just because she is in a wheelchair. The fact that she is "disabled" is just one characteristic about her. Do people give her time in order to get to know the real person? She has struck me as very, very intelligent, very sharp, very dedicated, very hard working, and very polite and friendly. She is a sweetheart. And I hope she succeeds to become a teacher one day.
Ignorance always makes me angry. People should not mock the disabled, whether the disability is mental, physical, etc. We are all God's children. Let's love and respect one another, and shelve the immaturity. Yes, we are all different. GET OVER IT. Show some compassion. (I speak to the general population, this is not directed directly towards you, young lady- the person who asked the question)
Let's choose the high road, and be understanding towards our fellow human beings.