Japan: "butt biting bug" video is huge

I am told that this video is a recent and wildly popular thing in Japan. Here's an English subtitled YouTube of "the butt biting bug song," Oshiri kajiri mushi. Video Link. It gives me acid flashbacks. "Tight asses and hard asses and beaten asses and shriveled asses." In what universe do these constitute appropriate lyrics for children's music?