Anyone who wants to tell me that they are not evil at their core can explain why they employed a murderous scumbag like Lon Horiuchi, and continued to employ him after he committed murder.
That is the FBI, not the ATF. Specifically their hostage rescue team.
They got a federal judge to dismiss charges against him.
They do it because they want people like that willing to pull the trigger whenever given the order to do so. If they start allowing them to be prosecuted then more will think twice when told to pull the trigger, and they won't be as effective.
So instead they defend their actions at all costs, and at the federal level with federal judges in your pocket, when actions are taken in the performance of duty as ordered by a superior there is not much that can touch you. You get the Nuremberg Defense in practice even if not officially.
If they let him get prosecuted, more agents will start thinking for themselves, and not be good little soldiers who jump when they say jump and shoot when they say shoot. That is counterproductive to a paramilitary team's effectiveness as a tool of the government.
The FBI is big and there is a lot of good people in it. But sometimes what gets done in a big bureaucracy is for the good of the bureaucracy and not the people they serve.
The HRT was called in by other agencies to come in as a team of commandos after other federal LEO were killed, certainly without full understanding or maybe even much care of what led up to that as it doesn't change the mission, and given a lot of discretion to respond accordingly.
In modern times they are much more successful with media blackouts, use cell phone jammers and block internet and land lines during such crisis. So such big spectacles noticed by most of the nation will be very infrequent. Similar events still happen though.