It's whether that dancing penis is right there where any unsuspecting person including a small child or an old lady can stumble across it with no warning, no door to consensually pass through.
I'm sorry, what exactly is going to happen if a small child or old lady happens to stumble across that video? And how far do you take not allowing something that could potentially cause offense that someone could stumble onto?
EDIT: And what is a "small child" doing surfing Vimeo without their parents/guardians present? Or does your definition of "small child" include older children? And are you going to tell me that a woman who is an "old lady" has never seen a penis before?