No, what you
didn't do was actually go to a miscarriage support board and harass them. What you
did do was laugh amiably about the idea that your friends would act as if you had, as a joke at your expense. You found their joke about miscarriages funny and reveled in it; ergo you joked about miscarriages.
Which, for the record, I don't have a problem with in this specific case. I also don't have a problem with lumberjim's indirect reference to making fun of black people without actually making fun of real black people.
Face it, you don't have a leg to stand on in this argument--
oooh, wait, you're not paraplegic are you?