In general, I don't think limiting the power or size of the government is the solution, although I'm all in favour of shrinking certain parts of it in very specific ways: You can make your prison management arm smaller by privatising jails and prisons, but you haven't really fixed anything if you do that; on the other hand, I would be delighted to see defence and policing budgets the world over diverted into infrastructure, schools, and housing, and there are many very good examples of how those can be managed well by both central or local government.
If the government is unaccountable, then anyway it's useless to talk about its size, it can simply accrue more power. I think America is especially (although not uniquely) feeling the pain of lack of accountability at the moment, not least because the electorate as a whole is increasingly misrepresented by the outcome of elections, there is no culture of building political consensus, and as a result every vote becomes a zero-sum contest.
It does not have to be like this.
The problem with this argument is that, although it is right (I agree!) it will not carry the debate.
_The_ problem here is that there is a large group of political moderates who trust authority. Arguing that the authorities will misinterpret and/or abuse statistical evidence will not sway their opinions.
It is difficult to convince that group to limit the power of government. The best argument I came up with was an appeal to a fundamental right to privacy; but that has pretty much all but evaporated in today's world. Privacy is too expensive and might be politically untenable. That argument started to collapse in the hysteria after 9/11 2001.