Is this Halacha? Why not take such a position to Beis Din? You should learn about things like Dina D’Malchusa Dina and Minhag Hamakom, and how they impact the actual rulings Beis Din would give on these things.
I mean just consider the consequences in refusing to do business with women as they need their husband’s permission. That would likely open the merchant to all sorts of legal issues. Would be very strange for any Beis Din to uphold such a strict approach (a strict “Din” approach to disputes is generally not how matters are resolved in Beis Din… and this FYI, is perfectly fine in Halacha).