Trust me I've seen plenty, and it does not bother me because it is their own personal choice to wear whatever the fuck they want. People who are overweight do not have separate rules for indecent exposure. They aren't and shouldn't be required to cover themselves up just because people like you actually think your feelings should be taken into consideration when they get dressed in the morning. If a man doesn't have great personal hygiene and his clothes are in rags, it's probably safe to say he isn't doing well financially. You don't know his story and you shouldn't be ignorant enough to assume that he's dressing that way out of choice, for all you know it could have been his last shirt.
You are old-fashioned thinking that your mid-section and lower back should be covered, you sound pretty akin to my grandmother to be perfectly honest. Whatever a persons weight is or whatever tacky tattoo they may have, it still does not give you any say in how they should dress. Others appearance has absolutely nothing to do with you and if you get this effected by seeing someone who you don't find attractive's body mildly exposed (which I'm sure no one would be complaining about if they were attractive) then you're the one with the problem, because you should not be this bothered about others appearance. It is nobody's business but their own.
Also he was threatened to get kicked off before he cursed, so clearly his baggy pants were a threat to all onboard.