I take it that you are saying that implying that dead people get buried is exactly the same in terms of offensive as implying that single mothers are promiscuous - have I taken you correctly?
I hate to have to spell something out like you're five years old but I'll give you a wee hint... It's not considered offensive because there is a single mother featured in the joke.
In the same way, that joke isn't considered offensive to centrelink offices, even though one is featured in it.
