I think pulses should absolutely be included in a vegetarian low-carb diet. They're high in protein and low GI, so they won't spike your insulin (which is the real GOAL of being low-carb), especially if you include a good amount of fat along with them. As long as you're not trying to go really low carb, there is no reason you should say no to 10-15 grams of protein simply because it comes along with 20 carbs. Beans are a really healthy food, so I would cut out absolutely every "excess" carb from my diet before I would consider saying no to beans. If you're doing something really low (like 40 carbs or less), then I would say you should probably cut them. Otherwise, they're fine.