Intellectually, it is absurd to say your position and chance did not play a role in what you became. You undoubtedly had a lot of help along the way. As I said hard work plays a major role too, but both are tremendously important. There are others who have worked just as hard and maybe even harder, possibly even harder and smarter and might not have made it as far as you because they just did not have luck on their side. Maybe the guy who sold his business too early- right before it really took off- might be a good example. I have a feeling you won't agree with me on this point though, but I just ask that you at least consider that it is potentially true as I take yours to be potentially true. Because either way neither you or I have empirical proof.
What property rights is Sumner trodding on? Seriously, he just views the limit different than you do not even necessarily further against private property rights than you do. Again this is your opinion and that is his. As for the government's agenda, anything it does (or does not do for that matter) can be described as it's "agenda" if one so tries.
Virtually everything I responded to above and you posted in response is opinion though and not anything real. Now trying to get back on topic, what is your response to my claim that a progressive income tax system is about just as abuse-prone and easy to calculate inherently as a flat tax system is? You did not respond to that part of my post.
Also, do you think value is what matters in taxation or nominal dollars? And if it is the latter, you are okay with the rich paying less value (to them) in taxes?
I have limited time at the moment so I'll just address the first item.
Your example of the man that sells his business just before it took off is exactly the type of example Sumner would use, or any person that believes in "luck". It assumes the success would come to the business no matter who the owner was, if the first owner had just hung in a little longer, the success would have been his. Thats not reality.
Reality is that when the first owner sells, it is because he has reached his limit, he is tired, he sees no future in the business, and he wont' or can't invest any more into the venture. His attention is no longer focused on making the company a success, but on getting out from under the burden. He may have done his best, but it wasn't enough. It is much more likely that no matter how long the first owner keeps the company, there will be no success for that company.
He sells the business to a new owner that sees a future for the struggling company. The new owner brings new ideas and new energy and new life into the company. It still may fail, but it has a chance to succeed.