One stated that anyone who was so deluded as to demand rights for animals had renounced their own right to be classed as human, and deserved to be hunted down and shot like the critters they anthropomorphised.
The other was a link to a newspaper article about a cat found with its leg pierced by a park railing. Police believe it was done deliberately.
If I found myself on a boat with a man who impaled cats' paws for fun, I would not hesitate to rescue my dog in preference. Which implies that I care more about animal than human welfare, which opens up a whole new can of morals.
In a broader sense of 'why', the question has been bothering me since it was first posed me in an email almost a decade ago. I also studied Ethics at university, and this was just the sort of stinker the examiners liked to ask. Our exam papers didn't have radio buttons, however; we had to write two-page essays to justify our decisions or lack of decisions. Consider yourselves lucky!
There are, of course, endless permutations on the theme: what if the choice was between an ordinary, non-criminal stranger and your dog? Your child and your dog? Somebody else's child and your dog? What if it was your cat, rabbit, rat, pet snail, ant farm? Would the degree of crime committed by the man make a difference? What if he was going to be executed for his crimes at the end of the journey anyway?
Sooner or later, if you keep changing the parameters, you reach a point where every initial dog-taker would choose the human and vice versa. Personally, for example, if I were faced with a choice between a person who persistently misused its and it's and a dog, I'd pick doggie.