No, football (or soccer) players should not be able to use their heads as doing so can lead to serious brain damage over time. Bouncing a ball of of one's head for control may seem like a good idea, but these balls travel at high speeds and can cause significant damage.
Your head is the most delicate part of your body. Life changing injuries (like concussions, bone breaks, paralysis, and even death) happen now when its illegal to use your heads. Using your head would cause horrible injuries and it is too dangerous. It is in no way acceptable for young athletes to headbutt opponents