I philosophically believe that taxation is theft. However, I'm still for taxation, but only for pretty essential stuff. No tax money for high school/college, churches, museums, etc.
I did not see taxation as theft because is through taxation that state can build roads, health care facilities, schools, fight external aggression against the state, pay state workers salary and finance research for technological development. But some tax collectors are theft and they also stole from state.
If taxes are 50% of your income or more then I believe that is theft. It seems to me that the government spends so much money inefficiently. What is that but theft?
If I walk up to you with a gun and forcibly takes 40% of your money, is it theft?