I too, don't think it's ever worth the risk. It's not like 2 dogs or 2 cats having a scrap, or even a dog and a cat. One little snap and it's all over for the snake if it's young.
The only interaction my brother's coastal Hydra ever had with my cat Indy when he lived with me was when she watched him through glass (he actually would come up to the glass and was very enquisitive when she was there) and I must admit, it was always fun to watch Indy's reaction to Hydra (especially if I touched her on the back, she's jump a metre in the air - cats are hillarious to watch sometimes) but that was the extent of their interaction. Hydra was very confident and always came up to see Indy when she was at the enclosure having a squiz, was never afraid of her at all, but it's just not worth the risk.
When our pythons come out for socialising, I don't think it's unfair for the other animals to be moved out of the room. Each can have their turn safely.