It would be just as stupid to tell a girl that she can't like male characters. Oh but wait- society pushes all of us to admire the male characters.
All main characters deserve the limelight. Black widow action figures shouldn't be a problem. The entire cast of Big Hero 6 on bedsheets- why is that a problem!?
The majority rules aspect of marketing is skewed and rather than giving children what they want, is telling children what they should want.
Fuck that.