Does luring a beloved lion out of a sanctuary so you can kill him for your own amusement make you a man? Does killing any lion anywhere make you a man? Lions aren't exactly encroaching on suburban neighborhoods like yours or mine and threatening to eat our children or pets, now are they?
Lions aren't tearing around in trucks waving black flags and shouting "Death to Americans!" They aren't going on social media to spew hatred and incite violence in the name of their god, now are they?
Don't we have real bad guys to fight? How about you focus your desire to fight to the death against people who traffic women and children as sex slaves? How about you aim that killer instinct against mass murderers who are still on the loose? Maybe go after people who want to commit mass violence against Americans in movie theaters or against Marines or policemen?
I'm not in favor of vigilantism but I'm also not in favor of what you did to that lion. You looked so proud of yourself when you posed for a photo in front of Cecil after you killed him. You disgust me. You are not a man. You are a rich killer who happens to be a dentist whose practice has now closed because your patients are disgusted by what you did and have found another provider.
Karma's a bitch and you're not a man.