If they try that, then guess what happens.
1. Most people will (rightly) come to the conclusion that they are hiding something that they don't want Barr to uncover.
2. They will also seem petty and desperate.
3. Possible obstruction of justice charges against them. If you loons have been (wrongly) saying Trump obstructed justice by firing Comey, then why isn't trying to remove Barr when he's in the middle of an investigation also obstruction? Yeah I know, logic and DUmmies are about as far apart as east and west and all that, but still... Many people will see the parallels, which goes back to point 1.