I think what Thomas was trying to address is those folks who don't follow common rules of decency "around the ship."
I have walked away from a buffet line when a man of the sort Thomas described shows up in the line next to me. Complete with icky, hairy armpits. Wearing nothing more than swim trunks and a singlet.
Sure, it's his cruise and his right if he's following the putative rules, but it kind of ruins MY appetite.
Putting on a shirt when out and about is no big deal.
I think the issue is that simple. It's about respect for others' sensibilities.