You are forgetting the fact that Rakghouls are also inside facilities and building and swarm rather quickly. The threat is not in the fact they are animals, but that they seem to be limitless and only need to touch you once to make you one of them.
I would agree if they were just a really dangerous animal (like a lion) but rakghouls have features that most animals we hunt on Earth do not.
You don't see a pack of lions swarming your jeep in Africa from the tall grass and turn you into a lion if it grazes you.
Disease, regardless of type, is only an issue if it's untreatable. The rakghoul plague isn't. Revan and... a doctor whose name escapes me came up with a cure three hundred years ago. The Pub-side Four and another doctor whose name escapes me managed to replicate it within a week of leaving Coruscant. If you go lightside it's even pressed into production almost immediately and through altruistic channels, so it's pretty clear the Republic has the resources to mass-produce and distribute it; by the end of Republic Taris this is a first-world measles epidemic, not a third-world AIDS epidemic.
The real problem with the rakghouls is not that they can turn other species into ghouls, it's that they're apparently sentient now, up to and including having protolithic Sith in their ranks. This makes hunting them a far less simple affair than putting up a bounty and sending some droids around. Beating a horde armed with blasters and Force Lightning takes tech, training, and Jedi support.
On the other hand, it also offers the potential for a peace treaty, which isn't an option with an animal infestation or viral epidemic. So there's a sliver of hope there too.