“One would think that most FBI agents would have already resigned.”
I suspect many have retired. Some have resigned.
What that does is ensure the department is more corrupted as their replacements are certain to be more politically correct.
Better for agents to stay in place and be reliable sources of information than to resign.
Of course, the FBI has been highly political since it came under Hoover, and it has a long pattern of being unconcerned with Constitutional rights.
Get ready for quite a ride with Donald Trump then. He’s going to make earnest cleanup attempts, but he needs a broom to do it with, and that puts the broom in a powerful position.