I own a pure Hog Island boa, and while I understand the opposition to crosses, I had my own reasons for choosing a pure line. It was important to me that my choice of boa remain relatively small (I had a BCC as a kid that grew to nearly 8' - wife wasn't down with that

) and had a calm temperment (so far, she's been very sweet). So for those reasons, for me, a pure specimen was a necessity. But I have no plans on breeding her, as she will be strictly a pet for the whole family to enjoy.
I think the biggest reason many are opposed to crosses (and Hogs in particular), is the muddying up of pure bloodlines that are rapidly becoming extinct in the wild. And while I understand that, the reality of the situation is that this particular snake WAS bred (as are many others), needed a good home, and you are providing that. How could that NOT be a good thing?
Best of luck with your snake!
RR_20 (Mike)