They have a right to rebut and get a fair hearing. There's a whole "Human Resources" protocol associated with all that, not unlike the process in any large organization. The person wanting the individual gone has got to have documentation--they can't get fired on a say-so.

If they're upper echelon, they tend to have fewer rights, oddly enough--when they want you gone, you're going. You might be able to string it out, taking leave and sick days, but eventually they will shove the bad apple out the door--if the apple is, in fact, bad and not being discriminated against.