I think both, and neither. It's shameful because they know it is illegal, and that it alters their mental state yet they do it anyway. If some salary man wants to do this, he isn't harming anyone but himself, really, unless he's on company time. But sumo wrestlers are highly respected, highly paid athletes in a very popular, traditional sport. they are in the spotlight and all that they do is scrutinized. that's a hard life, yes, but it's what they chose. they need to respect that, and realize that they are disrespecting not only themselves, but their country. alcohol is legal, but if an athlete decides to get stinking drunk all the time, that's shameful too. if it impairs his performance as an athlete especially. Athletes' bodies are their canvas and they need to treat their bodies with respect too.

in this situation with the marijuana, I don't think the shame just comes from the drugs being illegal, or impairing their mental state temporarily. they shouldn't be barred from having a good time ever, and everyone likes to have fun. the shame comes from what they are doing to the sport by bringing in something illegal, as well as something that has a stigma in Japan as a harmful drug. they've tainted the sport, as well as the tradition of Sumo in Japan, so that it won't have the respect it used to have by those who value the older ways. I know people say that times change, but Japan is one place that should really keep traditions sacred, even while also embracing some of western culture.