I'm based in the UK, and was assuming - perhaps incorrectly - that many of the commenters that weren't bothered by the word 'retard' were based in the US, where I believe that word has less of a stigma.

I honestly don't understand your comment regarding historical contortions, I'm afraid. However, I'll stand by the argument that the word 'retard' is used as an insulting term for a section of society - at least here in the UK - and, from that point-of-view, does echo words used in a racist context, or the context of hate crime (while acknowledging that using the word is clearly not a crime in itself).