Why should @miniyou64 refuse to use something they've been forced to pay for, especially when the government mandates that no alternatives are permitted to exist?
Taking something from someone via the threat of violence is either threat or extortion, period.
If you don’t pay taxes, the IRS will audit you and you will be fined and/or sued. That doesn’t strike me as a threat of violence. There are hundreds of legal ways to lower your tax obligation as well. You can also choose to elect different politicians who better serve your interests. Privatization eliminates that option.
You really want one or two private companies to own your roads? How do you collect money to run the court systems? Do you pay separately for fire and police protection? What about the military?