Just to break it down:
MAGA is a cult. As Trump is the cult leader, he trains (i.e., conditions) his followers to identify with him.
Trump is in serious trouble with the FBI.
In the seriously paranoid Trumpist mind, the government is compromised. (This can be any and all branches, any officeholder.) In this way, the offices are interchangeable as they all represent one thing, the government as a whole. The IRS and the FBI, by virtue of both being government agencies, are thus the same.
The FBI moved against Trump. The FBI generally are armed. Well, look here: the IRS just advertised an opening for certain armed agents. (Even Chuck Grassley is concerned about this.) Both carry guns? The same.
The IRS has the extraordinary ability to reach into a person’s everyday life. The FBI did that when they entered Donald Trump’s home (never mind it was to serve and execute a legal warrant). The IRS and the FBI, again, are the same.
SO NOW when Donald Trump rails against the FBI, OR if the GOP rails against the IRS, the rage is the same, directed at the same target (the US government, which currently manifests as Joe Biden and Merrick Garland as real people, not abstraction).
The violent extremists are thus encouraged to treat all of these entities the same and with the same venom and animus. All of this, so that they can remain identified with their leader.
FBI = IRS. Biden/Garland = US government. And MAGA member = MAGA leader.
All of this is done through the simplified “logic” of proof by analogy, a corrupted form of syllogism described as paleologic.
Several scholars decades back told us that, in addition to projection, fascists in their propaganda tend to communicate through association. This shows the power of that simple construction: because x is like y, x is y.
Bad logic. Cult logic.