For weight loss? Bread is factually bad. It's high on calories and has little actual nutrients. Eating similiar ammount of calories through meat or vegetables will give you a lot more valuable macros. Grains are pretty much useless calories. If you're just living your life then it's fine, but when loosing weight you need to limit the calories intake. When faces with much less calories to eat each day it only makes sense to ensure that the food you use them up on actually provides your body with more than just sugar.
Oh, I'm not arguing that high doses of carbohydrates aren't great for weight loss. I mean generally, as a general hypothesis the Palaeolithic diet doesn't stand up to scrutiny.
Yes, breads are bad for weight loss, but so are equivalent amounts of potatoes or high starchy vegetables.