I don't think jug6ernaut missed the point whatsoever, and I wouldn't characterize him as nit-picking either: The question of who is expected to understand the t-shirt and what its point is (as compared to an unbranded t-shirt) are perfectly reasonable. Personally I see nothing wrong with t-shirts which can only be understood by an "in" group, but that doesn't mean that there's anything wrong with asking if that was the intention.
Your reply, on the other hand, strikes me as exactly the sort of knee-jerk defensiveness which often makes me wish that submitters couldn't comment on their own posts: Not only did you fail to answer the question, but you implied that jug6ernaut was being unreasonable to even ask it.
It's your site and you're entitled to encourage and discourage whichever types of posts you want -- but I think if your desire is to have a site where people engage in meaningful discussion, you made a poor choice here.