You did the right thing by not allowing the rabbit to suffer.
Regarding the pictures and video, I feel you did what was appropriate in warning everyone that they were graphic. After that it's up to the individual to view the pictures/video or not, knowing full well that they are graphic. I chose to view the pictures and not view the video.
The people that are complaining about your pictures/video remind me of the people on YouTube that complain about the graphic nature of videos showing snakes eating live prey and they also know full well what's on the video before viewing it. Yet they choose to watch it and then complain about the graphic nature of it.
I guess people just need something to complain about.