Some people simply don't have the money spare. To be very honest, if I was in financial trouble and would have a family to feed and somebody would give me the choice of killing my pet or pay a damn load of cash for surgery I would choose for killing it. I'm not saying I wouldn't be sad (such a thing happened to me before actually, and I was beyond sad...), but if you can't afford it there's not much more you can do. Unless people are willing to help, but people often can't be arsed to do so, so who's the bad guy then?
Please don't be so single minded... it's not like the guy killed his pet.

It's the American healthcare system I despise more than that guy, actually. If you're not able to afford your treatment, then you're screwed. >_<
Anyway, I don't know what situation this guy was in. If he was in a situation I described earlier, then I don't really blame him. If he actually did have the money spare, I think he's stupid.