I think it’s mostly bad because there are very sharp little chrystals of calciumoxalate in it, and that is sth that causes irritation to the mouth and possibly throat and/or gut lining. It’s not the toxicity thats worrying but the fact that the mucosa may swell and there may be difficulty breathing. It’s good that you’ve given him broccoli and snacks. How does he appear? How long ago was it?
Edit: looked it up now and in a person, there could be vomiting if enough material hit the stomach. Since a bunny canä’t vomit for physiological reasons, I think you should call your vet if you’ve a good exotics vet, and ask their advice. I don’t know if bunnies ever have their stomachs pumped out but since he can’t vomit, there would be no other way for him to get rid of the irritating agent. Bunnies as you know have sensitive tummies.
It’s quite possible that he will be fine on his own, but I’d not chance it. Dogs and cats and people are generally fine in 24 hours with no treatment exept symptomatic (if there’s difficulty brweathing) but bunnies have peculiar tummies and GI tracts.
Please report back!