I might be wrong and the brother might just be a mindless asshole, but I think the brother is lashing out as a way to give her tough love. He's probably concerned as all hell and doesn't want her to go down this path, she's his younger sister after all. Older brothers do that sometimes, not all of them are sweet and gentle. Men do that in general. Personally I feel like that type of love is lacking nowadays and that's why people in general, mainly women, are so soft and overly emotional.
Almost every strong confident women I met grown up in an environment where people didn't sugarcoat things.