Active enemies only stop you from doing the Encounter, Quest and Camp actions (check the Quick Reference sheet on the back of the Rules Reference book). Movement, Exploring, and Fighting are allowed when an enemy is present.
When you Fight and you or the enemy has the Ranged ability, both parties inflict damage as normal, except when one party does not have the Ranged ability, which causes an additional damage to be inflicted on the party without the Ranged ability. Ranged allows the Fight to occur between parties in adjacent spaces, but does not prevent a party from inflicting damage if it does not have the Ranged ability. It's just an oddity of how the rules work.