You're lucky you didn't get the hell out of you, don't mean that as an insult, just saying, down here, people take geneology seriously, especially in the older cities. To say something like that is akin to insulting someones family, cause in fact, by going after their heritage, you are.
It was a joke. No such t-shirt exists, as far as I know.
But in the immortal words of the J. Geils Band -- First I look at the purse.