My mistake, I remembered it incorrectly. It was Aisha's sister, Asma, and Mohammad did kind of impose his opinion.
Sunan Abu-Dawud Book 32, Number 4092: Narrated Aisha, Ummul Mu'minin: Asma, daughter of AbuBakr, entered upon the Apostle of Allah (peace_be_upon_him) wearing thin clothes. The Apostle of Allah (peace_be_upon_him) turned his attention from her. He said: O Asma', when a woman reaches the age of menstruation, it does not suit her that she displays her parts of body except this and this, and he pointed to her face and hands.
Aisha's sister was still ignorant of such a commonplace custom? It still seems like an extreme case, "cover yourself, you're turning me on", kind of thing. It also seems the modest attire is so extreme because those that did dress modestly in Arabia covered all but their hair and face, which was mostly a custom that came about due to the climate. It's pointless and a stumbling block on Islam to impose desert attire for every climate when societies are perfectly capable of determining what is modest for them.
So if one tells his daughter to dress in a certain way its like saying you're turning me on? Since this is how you talk about prophet Muhammad peace be upon him, you will get a frank answer.
But before that, the second thing is hijab is not a "custom". Third, the hadeeth was in the early days of Islam.
Fourth, if it were only a custom as you say
A) it wouldn't have been ordered by the messenger of Allah and B ) It wouldnt be connected to age. C ) If thin clothes was because of heat, then it cant be said that covering was because of the climate. D) It mentions not "displaying" parts of the body.
On top of this, theres disputes about its authenticity (although theres other authentic ones with no dispute and with similar meanings). Because A) its chain is disconnected, and B) it has Saeed Ibn Bishr Al Azdi in its chain, whos hadeeth is not accepted by many scholars, and also has Qutadah, whos narrations arent completely trusted due to what is called in sciences of Hadeeth, Tadlees (Mixing between words of what was transmitted from the prophet and words of yourself)
So please, if you don't know much about the issue its better to either humbly ask, or not say anything, its better than using some expressions you did. This issue in particular isnt debatable and never has been over 1400 years. Books have been written about it discussing hundreds of narrations.
Even in Christianity theres verses about women covering their heads in Church.
But every woman that prayeth or prophesieth with her head uncovered dishonoureth her head: for that is even all one as if she were shaven. For if the woman be not covered, let her also be shorn: but if it be a shame for a woman to be shorn or shaven, let her be covered." 1Cor. 11:4-6. Theres also verses about it in the OT.
If you choose to think they shouldnt follow that and their standards of modesty is better than standards set by the Bible, then let it be. We just dont do that. We hear, and we obey.