jokes are often simply a generalization of parts of life.
This joke was no different
I am sure the two headed incestuous Tasmanians or the sheep loving Kiwis or even the no tooth unmarried feral Collingwood supporter has a right to feel aggrieved however most people fortunately react to the comments or jokes based on the manner they were delivered and the intent of the content and not literal demeaning aspects of it.
Not many jokes around that are not at the expense of another person or group.
