I gotta agree with Kenan on this one. Using 'retard' is no different to using the word 'gay', they've both become commonly accepted to mean something else in certain contexts. Of course not everyone will feel comfortable with the use of that word but the same thing was experienced when people started to use the word 'gay'.
I've used the word 'retard' and never connected it to the mentally disabled. Speaking of which 'disabled' is also being used as insults these days, and I know the majority of the people who use it that way (at least the ones I know) don't mean it as an offence towards the disabled.
Thats the thing - I am not confortable calling people disabled or handicapped, if they say something silly or have a funny way of walking/talking either..
It's just another figure of speech, and something that comes down to context.
I dont know why the word context keeps being brought into this. I know you lot arent suggesting calling a disabled person retard lol.