It happens way too often, IMO- vets are often more heavy-handed than I like to see- they're determined to "get the job done" & don't have much time, but snakes are fragile when it comes to this kind of stress, & when you couple that with injections or other things they may see as necessary, I would just personally try to get him stronger first, & maybe you'll never even need the vet's help. If it means taking a guess on a fairly-safe dose of Panacur or Flagyl to get his appetite up & his GI tract functioning better, that's what I'd do. I find that "TLC" works best for snakes- they survive all sorts of things in the wild, but few things are more stressful than vet care for an imported snake.