"Not a good cultural fit" is such a passive-aggressive way to justify firing someone. It's basically saying "You can do the job, but we're stopping you from being able to do that job, and we're going to justify it to ourselves by invoking 'cultural fit'".
> When you’re in a job that you’re not a good fit for, you’ll start feeling things like “nobody listens to me,” or you’ll notice that your manager doesn’t seem to appreciate your work or your work ethic. Sometimes your manager seems to be acting weird around you. Sometimes your manager asks you to change your attitude, and you do change, but it’s like they can’t see it.
In such a situation, I have to question whether it's the employee who's doing something wrong or whether it's the company that's doing something wrong. I mean, if your manager gives you feedback, you take their feedback, and they don't notice the difference, it certainly sounds to me like the manager wants you to fail.
I'd recommend the OP read about "Set Up to Fail syndrome": http://hbr.org/1998/03/the-set-up-to-fail-syndrome
> We’ve let go of half a dozen employees and kept only as many, and in every case where we let someone go, that person has gone on to work on things that they are more passionate about and where they have excelled and been happier at.
Wait, so you fire half of your staff and they're happier afterwords? Again, I have to question whether it's the employees' fault or the company's fault. If half of your staff is leaving to places where they're happier, what does that say about the company?
> Sometimes you can detect a cultural mismatch within the first two months, sometimes in the first two weeks, and perhaps even on the first real day of work. It can be so easy to justify keeping the wrong employee on staff that a decision to fire an employee can drag on unresolved for months or years.
It can be so easy to justify firing someone when all you have to do is throw around the words "bad cultural fit". How about giving concrete reasons why the employee wasn't working out? That way, you don't have to sit around and guess when you're actually going to "detect" a "bad cultural fit".