"Yes, and also, under that scheme the contributors would not get their portion of defence taxes back."

Yes. The contributors would pay money, get some money back because of lower taxes, but have to cover more of the overall cost of defense than their non-contributing neighbors. That is the essence of the free rider problem.

If everyone voluntarily contributed their portion of their current defense tax bill, defense costs would be fully covered. Furthermore, this supermajority could vote to eliminate involuntary taxes to pay for defense, once the money was collected.

So the government is not stopping Alan from transitioning our democratic government to a system of private support of the military. The free rider problem is.

Therefore, the reader is asking a very legitimate question. Is Alan willing to hold a gun to a neighbor's head (with help from his "buddies") to extract $4000 to defend the neighborhood.?

Alan says "no" to this question. But when there are free rider problems, his actions are saying "yes".