Government is imaginary?
The same could be said of "family". Or "society". Or the NRA. Or any group.
There are only individuals.
However, while a group is nothing without individuals, individuals become "more" within the group. That "more" may be positive or negative.
Seeing yourself as a part of a group can give you courage to do things you would never think of doing on your own. It might give you the courage to mount an effort to collect coats for poor people, or it might give you the courage to join a middle-of-the-night armed raid on someone's home.
The "collective" has a real-world effect.
It also has an effect on those who are not a part of the group.
It can be discouraging to see individual members of a gang attacking others with no consequences. It can be discouraging to see what happens to their targets who fight back. Bad guys find safety in numbers. And the biggest numbers are found in that coercive, violent gang known as government.
Government doesn't exist apart from bad people willing to do what they believe government is empowered to do- the belief that belonging to government empowers them to do things that are forbidden to non-members- and those individuals, and their beliefs, are a danger to those who find themselves in the cross-hairs. Ridiculing the existence of government will only get you so far.
While I could fill this blog, every day from now on, with individual examples of evil committed by people who only have the courage to commit the evil because of their membership in The Gang, that would be tiring, and no one would want to read that. So, the shorthand of referring to the evils of government is useful.
In the end it comes down to individuals initiating force and theft. But to ignore what motivates them, emboldens them, and helps them escape responsibility is to ignore the elephant in the room. As long as most people see government as a real thing, apart from the interchangeable individuals who make it up, you will keep needing to address that belief.