FBI Oath of office
"I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God"
Purpose
The FBI's mission is to protect the American people and uphold the Constitution. The FBI is a national security and law enforcement agency that uses, collects, and shares intelligence.
The Agency as a whole is neither fulfilling its stated purpose, nor are members of that Agency abiding by their oaths of office.
Of course they will fight Trump at this point. Their careers are on the line.
AI and search engines do not give results for a specific oath of office for the Secret Service, instead directing the searcher down a bunch of generic rabbit holes.
Smell the stink yet?