Well, I've determined that there are people that are hell-bent on saying that t-shirts are underwear and are immodest.
But I found a website in my investigations into this somewhat laughable accusation. (Keep in mind, I view a t-shirt as a tunic type that is not form fitting and comes below the waist.) I found a good use for your immodest t-shirts. Of course, the woman on this website doesn't go long enough with hers, but you can make them longer. She details how to turn those immodest T's into a skirt. Make it longer, and voila! You have a pretty skirt that costs you $0.00.
Enjoy!