Everyone in FedGov can be fired. There are mechanism to do that.
My solution is easy. Make them resign.
A TAD assignment for three or four months to the new office in Severeboondocks Nigeria or Russia or Moldovia should induce resignation
I spent 36 years working for the federal government and was a member of the SES. It is extremely difficult to fire a federal employee. It is a long, drawn out process.
For example, if you want to fire someone for poor performance, you must produce documented evidence and show that you have conducted counseling sessions to show that you tried to help the employee improve his performance. The annual personal evaluation must demonstrate a long term record of poor performance. The federal labor unions provide legal representation. It consumes lots of time and effort for the supervisor.
There are very few federal employees who are fired. I only was involved in two instances in 36 years. It took more than a year in both cases.
Regan did it to the Air Traffic Controllers.