First of all, I completely understand that sometimes the word slips out unintentionally during a conversation. I don't hold a grudge on others who use the word on accident, and can recognize that it was inappropriate. However, looking at the definition of "retarded" in Merriam-Webster (or any other basic dictionary) reveals a "slow or limited... intellectual or emotional development or academic progress." This has now been altered to replace words like "dumb, stupid, dull, lame, etc" and essentially labels those with intellectual disabilities as having those characteristics.
Clearly, members of the disabled community do not fall under such a negative category, but the misguided use of the "r-word" continues to hurt that community. Like I mentioned earlier, I don't feel any hostility towards others who use the word, as long as it was unintentional. In that case, increased awareness and understanding of the misuse of the word may help strengthen the relationship between the disabled and non-disabled communities. That's why it's so important to remove that word from one's vocabulary, and for the media to be more aware of how harmful that word can be to others.