I have to say, you could argue that the whole song is pretty offensive now to our modern ears, although I confess that mine are not that modern. First, it suggests that elephants are only really valued for their ivory tusks, for making billiard balls, albeit through the use of irony. Secondly, each verse belittles a common human mental illnesses such as amnesia/dementia, hysteria/anxiety and schizophrenia, with the latter wrongly stereotyped by split personality disorder. I know that their songs can still go down a storm with those of us of a certain age, but comedy has also moved on since the 1950s, and clever though their use of language was, you can rarely get away with a one-joke comic song these days.