If you hired a boat which had a dog on it the previous week I don't think you would be very happy if it had left some tiny creatures on board, quite likely where you sit or sleep.
I am a dog owner myself but totally agree that they should not be allowed on board in the same way that they should not be allowed in any eating establishment.
I was once having a meal when a woman came in with her "little darling" and proceeded to put part of her meal on a separate plate and allowed the "little darling" to eat it whilst sitting on her lap........DISGUSTING !!!!
Jeff