I think rabbits should be kept away from all garden plants, considering the safety of both rabbits and plants. Rabbits have a great appetite for various types of plants so they will readily and happily munch on most of them, causing significant damage and often completely destroying them:
This long-eared animal possesses a voracious appetite for all kinds of fresh vegetation—woody plants, perennials, annuals, vegetables, and berries. In fact, a menu of rabbit favorites is so ridiculously long that it’s easier to list the few plants they don’t enjoy.
Also I don't think keeping your rabbits well fed would be enough to prevent them from damaging the plants. Rabbit's teeth are constantly growing all it's life and for this reason they are biologically compulsed to constant chewing - and specifically chewing plant matter.
Rabbits are widely recognized as agricultular and gardening pest. Somewhat crude and unreliable but nonetheless illustrative way of showing the scale of this problem could be a comparsion: googling the phrase "rabbit pest" returns around 58 million results, while phrase "aphid pest" returns only about 11.7 million - and keep in mind aphids are one of the most destructive insect pests on cultivated plants in temperate regions. Of course the reason for this scale is not only large damage-causing potential of rabbits, but also their huge fertility rate.
But not only do your rabbits pose significant risk for scarlet runner bean plants, but also vice versa.
Scarlet runner bean plants pose a risk of poisoning. Its seeds contain phytohemagglutinin which is carbohydrate binding protein causing toxic effects upon consumption in monogastric animals like rabbits. For the same reason humans shouldn't eat raw bean seeds.