None of your business!
You’ll notice that the weightlifting section of a gym is dominated by men. But that’s not a good reason to avoid it. She was admonished by another gym-goer as she sat on a weight bench executing free weight chest presses, which annoyed her.
He said that, based on her “biology,” she shouldn’t be lifting anything more than 20 pounds. To say anything like that is not only stupid, but it is also quite rude.