"Is it true that some writer for the Huffington Post refer[r]ed to her youngest child as a 'retard?' "

Apparently so, or else he used the word "retarded"; it's not clear which. I found this: Huffngton Post July 3, 2009 apology by Erik Sean Nelson ...a sort of backhanded apology in which he again uses the offensive word:

<>"I wrote a piece making fun of the fact that a Trig Palin joke was given as the reason that Sarah Palin left office. I wrote jokes that were offensive but my intent was for them to be ironic and therefore not offensive. I was wrong. Within ten minutes of my post I received some emails from the loved ones of the retarded and I saw that my piece was hurtful. Therefore, I removed the post right after receiving the first 2 emails.

"I removed it immediately because I saw that it did not come across as I intended. I apologize to all of those who were offended."