A common belief amongst many people is that all Asians, or a particular Asian ethnicity, usually the Japanese, are misogynistic creeps who are obsessed with soiled underwear. Occasionally applied to other types of Asians, but usually to the Japanese.
This is, of course, not the case, but there are reasons why the belief exists. Firstly, many things that westerners consider weird are thought of as mostly harmless in Japan. The Panty Shot, for example, was originally used to show a character's innocence, or just as a form of humour, and was not intended to be sexual at all.
Also, Shinto, Japan's native religion, and many other Asian religions,have a very down to earth view on sex: it happens, it's necessary, so enjoy it. The Japanese creation myth involves the literal birth of the universe, and doesn't try to pretend it was produced by any method oher than sex. Likewise, the Japanese general opinion on sex is that it is nothing to be ashamed of, just as long as you do it discretely.
Often when westerners hear about things like this, they assume it must be because "those filthy Japs are downright depraved" and also make no effort to consider that the Japanese might find some western culture perverted or weird. Not helped by sensationalist media trying to make a story, or worse, people taking a joke story seriously.
Compare All Anime is Naughty Tentacles.