I'm going to fight against a guy requesting vacation
What makes you want to go against a man's vacation request?
I hate people who want a lot of vacations when they never work hard.
People need time off to recharge their batteries and you denying them vacation just to be spiteful is bad for business. Give people their due and approve the request.
I just fired him to give him a taste of his own medicine.
You shouldn't have fired him because you are angry. You open the company up to legal liability.