Vise Man one said that
A key that opens many locks is a good key, a lock that opens for any key is a worst lock..
Humans aren't locks neither keys, so objectively wrong, plus all you're saying with that phrase is that sexism is good.
To tell u the truth - if woman is used goods then man can be used goods too. That's all i wanted to say. Oh but in this manga the slut is agawa cus she fuck anybody and she is getting fucked by randoms. Facts wont change here.
There's no such thing as "used goods" unless the person is a retard obsessed with virginity and "purity", because almost everyone had a relationship once, that by itself would make someone "used goods ", you don't need to be a slut for that.
What facts? People are free to have as much consensual sex as they want, nothing wrong with that.
And what nonsense you're talking about when saying she fucks random people? She literally has sex
friends, just because we don't see the characters that doesn't make them random, for she to be fucking random she would be need to be fucking people she doesn't even know.
Edit: just point of how key and lock analogy doesn't work in real life, sometimes keys identifies as keyhole, and some keyholes as key