My last thought on the matter...
Yes, "just because it can be done doesn't make it right"... but, who decides what is "right"? Unless it involves crime, I don't want someone deciding for me what is wrong or right.
Yes, it is reasonable to assume all the points you made. But, if something is possible, there is the chance, however small, that it could happen in nature. Evolution is affected by small probabilities (mutations) producing creatures that are more likely to survive, though it takes a long time, and the dice don't always roll to all possible results.
Sure, it's not likely (hog island mating with a surinam in the wild), but it could happen. Just because you or I don't think something could happen, doesn't mean it won't. I'll take the low road and point out 9/11 (no one anticipated that sort of event as being probable).
And, I have to disagree with you about the other arguments (dogs/wolves and even cars) not being applicable. The arguments cannot be COMPLETELY applied, but sections of those arguments do hold water in certain aspects. For the dog/wolf argument, it's not the *same* because the domestication of dogs from wolves occurred over thousands and thousands of years, while the breeding of boas in captivity only began decades ago.
But, there was a study done a few years back about the domestication of fur foxes. On some fox farm, silver fur foxes were being raised. Breeding was determined by quality of fur only, and the little buggers had pretty nasty temperments (especially after they became adults), despite interacting with humans every day. This matched behavior of wild foxes that were brought into captivity.
However, the study started breeding some of these foxes for disposition (ie, breeding foxes that weren't quite as nasty with each other). Within a few generation, these "nicer", more domestically behaving foxes started displaying WHITE markings that NONE of the ancestors had. The point was that perhaps our domesticated dogs started displaying white markings in the same manner, somehow white markings and tractable behavior being genetically linked.
So, you have a new "look" appearing that separated these foxes from their wild counterparts, within a few generations. I might add that the foxes being bred together were NOT from different locales or phenotypes (they were all silver fox). That study may be more applicable than the wolf/dog argument.
Is domestication wrong, in your eyes? Yes, pure lines of rare animals should be preserved, but if people want pretty, easy to handle pets, is that wrong? Not to me. It's just two paths of animal keeping. "Pet foxes" that were well behaved would not be an attempt to save their species, but an attempt at domestication. Separate breeding programs to preserve the wild look and behavior of the species would have to be present.
So, bear in mind that the moment you choose a snake that is easy to handle over one that wants to bite your face off, you've started down the road of domestication, and who knows, even THAT in snakes could lead to different physical attributes in future generations.
Heh, I guess I always feel the need to argue with people who seem to want a "black or white" answer. I like shades of grey! 
Great discussion, and of course hopefully everyone agrees to disagree... 
-----
Lauren Madar - OphidiaGems.com | CageMakers
1.1 Ball Python, 1.0 Hog Island Boa, 1.1 Hypo BCI, 1.1 Surinam BCC, 1.1 Saharan Sand Boa