For me, a dancer is part of an artist's entertainment - 'backup dancer' isn't even in my vocabulary.
In 1930s mysteries, all sorts of motives were credible which aren't credible today, especially motives of preventing guilty sexual secrets from coming out. Nowadays, people sell their guilty sexual secrets.
When a person is humiliated, when his rights are being violated, and he does not have the proper education, naturally he gravitates toward terrorism.