I never stay silent when there is such a thing said.

I start off with explaining how offensive the term is, and that it is
not factual. If they truly do not understand, you will know
immediately that they did not by their reaction. An apology, or
expression of regret is what I look for.

If they still do not understand, I continue the factual discussion,
and explain that "retarded" is wholy inapplicable, using the
definition of the term and explain why developmentally disabled or
challenged, is more appropriate.

After this, either they get it, or they don't. At this point, I assume
that they are retarded, and point that out to them, then walk away.

There is also the person who will defend their use of the term. If
they do, then they deserve whatever they receive, and recieve they do.
If they cannot understand justhow much harder it is to parent special
kids, I have done such things as hand them my sneakers, and ask them
to walk a day in my shoes. I do not want them to go barefoot.

Most people "get it" with a gentle explanation. When they don't, I let
the fun begin.

BTW, I am posting way less, as we have serious issues at home which
are taking up a considerable amount of my time Some of the regulars
know what I am referring to). If you want a faster response, eamil me
at mark<dot>probert<AT>gmail<dot>com.