I have yet to hear a man tell me he was discouraged from entering some field (with the two possible exceptions of nursing and elementary education) by a woman, telling him 'boys aren't good at that'. (Fathers on the other hand are great for making sure their boys don't do too good at the sissy stuff).
On the other hand, I have directly witnessed math teachers and professors telling women that they needn't worry too much about understanding the class, "because you girls don't need it - you're graded on effort" (despite actually wanting to know). I've heard plenty of stories from women about being told "girls are bad at math, it's natural you don't understand". I've seen one little girl break down and cry because a man told her girls can't be engineers.
On the other hand, I have directly witnessed math teachers and professors telling women that they needn't worry too much about understanding the class, "because you girls don't need it - you're graded on effort" (despite actually wanting to know). I've heard plenty of stories from women about being told "girls are bad at math, it's natural you don't understand". I've seen one little girl break down and cry because a man told her girls can't be engineers.
There is a big difference there.