To the OP, I think able bodied women are perfectly as capable of standing as men. If either person had been eldlerly or handicapped, yeah, the other should've yielded the seat. In this day and age, there is no preferential treatment for a gender in every day interactions. If you're dating a woman, sure, treat her extra nice.
But, with your attitude (which I know you mean with the best of intentions) you're basically suggesting that women are not capable of standing, that they're handicaped in some manner and need extra help by virtue of their gender.
Mr Awe