It has to be pure otherwise why call it Capitalism?
It's like if you have a chocolate cake with a donkey crap on it. It doesn't matter if it's 99% chocolate, that 1% crap really spoils it.
If you accept that taxation is theft, you cannot settle for 1% taxes. It's like saying, people will still be robbed, but only a little bit. Either people should get robbed or they shouldn't, there is no gray area.
It's a black & white issue, based on moral principles.