I've kept two BP together and had NO problems whatsoever. I currently keep the following together : 2 Bredli, 2 Dumerils Boa, 2 Red Tail Boa, Yellow Anaconda and Half dwarf Burmese, 2 GTP, 2 Jungle Carpets, another pair of Jungle Carpets, more Carpets. I've NEVER had a snake try to eat the other snake. Never had them "fight " over anything. Never had ANYTHING bad happen. So yes, it CAN be done without anything bad happening. A lot of people who say "it should never be done" are just repeating what someone else told them not to do and most of those people are just repeating what they were told.
Problem with this is it only has to happen once, so why risk it? There is NO reason to house two snakes together except someone thinks it looks nice. There is no benefit to the snake, but a list of risks. Can it be done, of course. Should it.......