I absolutely agree. First of all, wearing a bra or anything else is a matter of free personal choice. No girl/woman should ever feel required, coerced, shamed, or otherwise mandated to wear a bra. Second, breasts have internal support structures (tendons and such) that can support the weight of the breasts, provided they were allowed to develop along with the breasts as the breasts grew. When a bra is always worn and always supports the weight, those supporting tissues atrophy and can no longer support the breasts, leading to sagging and a need for a bra when the bra was hypothetically supposed to prevent sagging in the first place (as the myth goes).
There is absolutely nothing wrong with a woman not wearing a bra. There is no reason for her to feel embarrassed, ashamed, or afraid to go without that medieval torture device lashed to her chest.