I would never fire an employee “out of the blue” unless it was for something dangerous or criminal. But not because I didn’t think they fit in or caused tension. If that’s the situation they deserve to be brought in and explained to what they are doing is wrong. You may have to do it twice. But if they don’t make an effort to improve then you can fire them and refer back to the warnings they were given. That’s the fair way to do it and you’ll have no regrets. But to yank the rug out from under someone who doesn’t have a clue is wrong wrong wrong.