how do i fire a drummer that everyone hates and who is not that good. But we don't have any replacement drummer (except our great friend but has never had a lesson and doesn't have a complete drum set) and the bad drummer gets all sad which makes the singer change his vote. Should I fire him or suck it up?
Just be like:

"Hey man, the band and I have been talking and your attitude just isn't cutting it. You gotta shape up and practice more. Or we're gonna have to reevaluate whether this will work or not."

If you're just done with him be like:

"This ain't gonna work man. Your attitude isn't working with us."

As far as bringing on your friend, I've tried it now with two starting musicians, one a drummer the other a bassist, it's tough as a mofo I would NOT recommend letting a new musician friend join your band... especially if they don't have the drive to practice... like my friends lol. If they're a driven individual who really wants to play then try it out with them for awhile.
Quote by sargasm
There are no genres in metal that end with "core."
If you guys can't get along, or don't like each other then he's got to go. If you can get along, then just give him a choice- Get your **** together or get out.
in my opinion id rather not have a band than be in a band with people i dont like so even if i didnt have a replacement i would boot him

but yea just say the band is goin in a different direction