Can I reject a guy bluntly instead of saying sorry I have a boyfriend?
That's cold, why would you say something bluntly instead?
I want to hurt his pride and he kept hitting on me.
If they were harassing you then you should be blunt. They obviously can't take a hint so that might work.
It's not cool to be direct but I am tired of being cool.
Understandable, especially if they had been bugging you for a while. You can be honest with people no matter what, you don't have to protect them with a lie if you don't want to.