OEJ:
Bring them over to a culture where women cover their breasts, and I don't think they'd be so keen on running around topless.
Oh you know better than to say that.
That's a terrible way to try to defend Bob's argument, if only because it fails to demonstrate any casuality between his statement and yours.
If clothing is a cultural norm, a certain amount of acculturation is to be expected. In most Western societies, complete nudity is frowned on or even illegal. Often, it's just too darn cold. And in an Islamic society, being naked could earn you extreme sanctions.
Furthermore, there are some quite reasonable (non-theistic) arguments to be made for the utility of clothes. They protect us from rain and too much sun. They warm us when we're cold. They provide handy pockets for us to keep our shiny things and credit cards in.
Appealing to some facet of Adamic conscience seems kind of unfounded. Furthermore, you must agree that in cultures where environment conditions and adaptions don't require clothing, historical records seem to show a marked lack of modesty (much of pre-colonial Africa, South sea cultures, Aborigines, Yanomani, etc). In cultures like the Masai, people build shelters and make elaborate jewelry wear, practise animal husbandry, etc, but they don't bother covering their breasts. It just doesn't seem to be a priority.
I can maybe see a case for people who have become Christians adopting more clothing but again, that doesn't necessarily match Bob's assertion which seemed to imply that everyone had been sitting about just dying to put on clothes until then. I don't see any evidence that allows him to assign a re-emergence of some hypothetical nascent conscience as a result. Why can't it be attributed to the fact they they have now been told that nudity is a sin, and that sinners are punished for eternity?
Dear oh dear.