There is nothing offensive about seeing religious t-shirts (at least in most cases), or bare feet (also at least in most cases, which vary from culture to culture), but there IS something offensive about drugs (unless it says "no drugs allowed," but some would rather do away with drug references altogether). In terms of bare feet, in this culture, we're not offended by it in itself, but there are "no shirt, no shoes, no service" ordinances put up everywhere; the "no shoes" part is presumably for sanitary reasons.