This is exactly my understanding after a lot of research. Some populations of animals aren't harmed in any way by in-breeding, and the various python species became the individual species by breeding with their local population rather than a more diverse group. This is how speciation works. If animals didn't split into sub-populations and in-breed, we'd only have one species on the planet, and it wouldn't be us. In-breeding was a huge factor in all the diversity we see in nature.
Humans can successfully breed with close relatives too. The problem comes in when you start doubling up bad recessive genes. Deformities wouldn't happen very often if we in-bred ourselves, but when they do it's so horrifying that we rightly consider close relative breeding a huge taboo.
An example in snakes would be breeding Spider x Spider or Woma x Woma. Get two copies of the mutated gene, and you're screwed. As long as you have no destructive recessive mutations present, you're fine.