I do understand the customers, kinda, if they are regulars and know girls are a a rare occurrence there, they might get startled a bit or decide to come back later. But that's just the thing, they will come back later, so why is the shop owner kicking up a fuss? Actually, kicking them out is downright illegal. No one would do that in real life.
And there are more products actually for women, even if often men buy them for their girls (or the girls just buy them online) so a shop that wants a completely male clientele probably does not exist.