Actually this is the new thinking on broccoli from Dr. Susan Brown:
Some people are concerned about feeding foods that cause gastrointestinal (GI) gas in people such as broccoli. A rabbit’s GI tract is not the same as a human’s and many of the foods that may cause gas in a human do not cause gas in a rabbit. The most common types of foods that do create havoc in the rabbit’s GI tract are those that are high in starch and sugars because they create a change in the pH of the cecum and eventually can throw the whole system off. The result can be serious GI disease. Foods that are notorious for causing rabbit GI problems when fed improperly are grains of any kind and legumes (beans, peas, etc). Even starchy root vegetables and fruits if fed to excess with their high load of sugars and starch could be a problem and should only be fed as a very small part of the diet.
From the House Rabbit Society website:
http://www.rabbit.org/care/veggies.html