If you don't believe taxation is theft then don't give the government any money and see how long it takes before the extortion begins. If you personally want to give the government money then go ahead and do so on your own terms, but do not impose your will with the threat (and use) of violence upon those who do not wish to give anything to government. The only "tool" the government has to enforce laws is violence, as that is the logical conclusion of all attempts to enforce the law. You'd could get whatever it is you want from government for far cheaper through an individual or private organization, unless of course what you really want is to control other people who are in no way associated with you.
I can understand to a point the Libertarian philosophy, but if it was taken to the logical conclusion, the end result would be no government at all (anarchy). Whether you individually partake of all the government services or not, you still benefit from them through protection from foreign invasion, disaster assistance, our world-class healthcare system (R&D often funded by grants), protection from criminals, assistance if your house catches fire, a modest retirement plan through Social Security, roads, schools, running water piped into your home, trash removed from your home, legal protection of PRIVATE PROPERTY, etc.
Sure, we could privatize most or all of these, but I don't believe that is always the answer. What would a private water company care if they tear up the roads to fix some pipes? Would they be responsible for damage to your lawn or house? How would a privatized military protect paying customers but not everyone else?
I for one do not want to live in a "Mad Max" world by choice. If I did, there's probably somewhere in the world I could move to that's like that right now (Afghanistan? North Korea?). I do enjoy the benefits of living in the USA, and I also contribute to providing those very benefits to others through my service in the military.
It is true in my case simply because if my employer did not spend on me what they were willing to pay me previously, I would go elsewhere. Changing jobs tends to give a good pay increase anyway, 6.2% less tax would ensure I see more of that pay bump. What someone else would do, regardless of the pay or nature of their work, or how much (if at all) they choose to plan ahead with is none of my business and does not justify the threat of violence required for the government to collect money they did not earn.
Again, I wasn't arguing against your case specifically, as you likely have an in-demand skill and are paid accordingly. My point is that the government needs to protect (most) people from themselves as has been proven time and time again.
SS is a plan imposed by the govermnet for people who fail to plan. Is it a perfect plan?
Nope, but it's better than none at all.
For further reading, here's a recent article on this topic from another "frugal" blogger:
http://livingstingy.blogspot.com/2015/02/make-social-security-optional.html