Hemp is a dioecious species: male and female plants are separate individuals. In a batch grown from seed, you will get both sexes, and only unfertilised female plants produce the harvest you are aiming for. Sexing is therefore not an expert nicety, it is a campaign operation on which the value of your entire batch depends.
Dioecy, and why it concerns you directly
Most vegetable crops bear hermaphrodite flowers: each flower contains the organs of both sexes, and the question of sexing never comes up. Hemp works differently: a plant is either male or female, and that split is settled at emergence, in proportions you do not choose.
Male plants produce pollen and no usable inflorescences. Their only possible contribution to your harvest is a negative one: fertilising your females. In a crop grown for flower they therefore have no place, and removing them is the rule.
