Because his friends may send it on to someone else who is not amused:
"The NSW Liberal Party yesterday sacked its candidate for a key marginal seat after learning of an obscene group text message, involving a goat, which he sent to local councillors as a joke....
In his SMS, Mr Pavier sent out a hoax message purporting to be from a video store, alerting customers they had outstanding videos. The list named bogus X-rated movies, one with a title involving indecent acts with a goat....
Mr Pavier was overheard protesting: "It was a joke, you know - a joke. It was an SMS. I sent it to my mates. It had been sent to me and I forwarded it on to some of my mates....
Mr Pavier had sent the offending text to friends over Christmas. It was passed on to fellow Liberal and Labor councillors.
Source