I'm not against it under 2 conditions:

1) it is known that the offspring are healthy(no inherent genetic disposition toward disease or other health issues). As far as I know, mules can be expected to be as healthy as any horse or donkey offspring and live perfectly long healthy lives, and fit this condition perfectly. I've heard that ligers(lion/tiger hybrid) have health issues, I think associated with growing too large.. If this is the case they would not fit this condition.

2) it is controlled so that the hybrid genes do not "pollute" any other population of snake. Some hybrids are hard to distinguish, especially if a hybrid has been subsequently bred into a specific species line. I wouldn't want to buy a corn snake whose great great great grandfather was a king/corn hybrid if I was looking for a corn snake.

So pretty much as long as they are not subsequently re-bred, I'm ok with hybrids that have no inherent genetic problems.