
I'll keep this short and brief.
The reason girls are are looked down upon for having lots of partners or sleeping with guys they aren't committed to is because girls are viewed as innocent and pure by society's values. This was primarily influenced by religion and man made cultural norms.
Girls who don't conform to those standards are both consciously and subconsciously looked down upon because that's how we were taught to think in our society.
The issue here is it's unfair to women that they have stricter expectations when it comes to sex. It's looked at as okay for a guy to have lots of sex. If that's okay then it should be okay for a girl. As long as a girl isn't cheating or playing people, a girl sleeping around doesn't hurt anybody.
A common response to my claim is the key & lock analogy.

A key that opens any lock is a master key, a lock that opens to any key is worthless.
That doesn't explain why it's wrong for a girl to sleep around. It only explains why it's an accomplishment for a guy to sleep around while it's not impressive when a girl does it.
If the lock is in good condition and when it has a suitable user, it only opens to that 1 key, that doesn't make it "worthless". It's a good lock.
If that lock still opened to many keys when bought then it would be worthless.
Using that same analogy here's my questions...

Q1: What do you think about a lock that's in good condition which normally opens to many keys, but when owned, only opens to one key?
Q2: What do you think about a lock that normally opens to a select few keys, but when owned can still open to multiple keys?
Q3: Which lock is better?
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