By keeping an open mind. It's ok if 90% of women want to just play with kids all day, and 90% of men want to play with guns all day. But telling, suggesting, stopping the other 10% from trying the other side is the problem.

It's inherently hard. After all, statistically 9 out of 10 will match your expectations, but you should embrace the outliers, help them understand, that they're perfectly okay, and capable of doing whatever they think they want, be it guns, C++, teacher, nurse, etc.