Yes, you should respect all the animals but I see nothing that the OP did as disrespectful. Live feeding is the natural way of doing things, and the rate of injuries to the snakes from live feeding corresponds with the irresponsibility of the owner and how they feed live.
Some snakes do not eat f/t. I have one that I've had for 2-3 years that still won't eat f/t to this day. That's just how they are sometimes.
If you think that it's cruel, then sell your snakes and start collecting stamps.