Ok the thing is, digimon don't have genders. This is clearly explained in the show.
HOWEVER, many many digimon are shown to be heavily biased towards one gender, usually by being portrayed with either a male/female voice and posessing (human) male/female characteristics.
This can be said to stem from the fact that humans created digimon in their own image, and humans need to assign genders to everything to make it easier to relate to objects/creatures.
tl;dr Digimon are genderless but can have some gender characteristics.