Please don’t tell girls “The boy who’s picking on you actually just likes you”
Even if it’s true, you shouldn’t teach girls to respect that sort of affection.
And you should definitely not teach boys that expressing their attraction to women through violence and disrespect is ok.
Telling your son not to “be such a girl” lets his sister who overhears the conversation know that being a girl is not a good thing and she should be sorry and ashamed of herself.
It also reminds your son that being a boy is better than being a girl and therefore he is better than any girl he will ever meet.
In russian if you cry you get called a cabbage. Vote to change “dont be such a girl to “dont be such a cabbage” say I.