You could also end up with some serious illness when you're young and in need of special care without which you don't have any opportunity to build that income you're talking about. Each additional person being able to contribute means another person has contributed to your economic wellbeing and a egalitarian society where people's opportunity is not lost do to bad luck.

I would argue taxation is only theft if the money is spend on extremely bad, costly and possibly corrupt policy decisions like US wars in Vietnam, Iraq, Afghanistan or even the war on drugs. Probably a lot of these policy decisions are influenced by lobbying from various industries and special interest groups. Follow the money.