“Sometimes practitioners find the chosen play of boys more difficult to understand and value than that of girls,”… “They may choose activities in which adults involve themselves least, or play that involves more action and a greater use of the available space, especially outdoors. Images and ideas gleaned from the media are common starting points in boys’ play and may involve characters with special powers or weapons. Adults can find this type of play particularly challenging and have a natural instinct to stop it.”
The Department for Children, Schools and Families advising nursery staff that boys playing with toy guns should not be discouraged. From a jolly publication called: Confident, Capable and Creative: Supporting Boys’ Achievements.