>They don't need the deception.
Why are they then lying about what the camps are for? They are vastly outnumbered by the populace and almost everyone of them are gossipers with biglips and zogphones living in cramped complexes. The word would get out. They would need to deceive the public. The least messy and more systematic genocide is preferable for the establish in SHTF.
>Do you know the budget of FEMA?
That has many assumptions. I'm not under the impression that the budget isn't going to matter and other agencies are going to get involved when chaos happens. They need only send dissidents there, not every American. They don't really intend on providing supplies for the political prisoners long term either. It doesn't justify a huge budget.
1. SHTF is stalled. The system keeps sending perpetual death squads door to door SLOWLY killing dissidents each operation, wasting man power, gas, and salary. Currently happening but not likely under SHTF unless they are a high target. In my opinion demographic replacement and circusbreads is the boring game plan. Too many potential lawsuits and repercussions for this to be a main strategy.
2. SHTF happens. The public panics, supplies run low, and the government is offering "help". The public wastes THEIR means and resources just to get to the shopping center for shelter and sustenance, or risk death. They lock or load up targets and suspected "terrorists" onto buses for fuel efficient transport, and condemned them to the FEMA CAMPS.
>unconstitutional gun confiscation operations
It is happening but that depends to a degree but in times of peace and blurry team colors. People might think, "The system is not targeting me." but if SHTF they might think twice. Any sighting of an unjustified killing makes true dissidents jumpy. Now image that in SHTF where no one trusts anyone, ready to flee at a moments notice, and then the cattle rushing to get their supplies. That is a logistics nightmare. That is also considering if EMS and police are bogged down that strategy may not work. The problem with your theory is usually they are not frequent events and don't add up enough for reliable systemic extermination.
Keep in mind we are talking about SHTF. It's better trick millions of people than fight them directly, especially in a state of panic.