I believe we have been "tax slaves" since February 3, 1913.
Our taxes have been incrementing upwards for the past 100 years. Inflation alone has pushed more people into higher FICA brackets. During that 100 years, many new taxes have been added at the Federal and local levels.
We have reached a point where the government has become our masters. Our masters decide how our wealth is used. We need to say 'enough'. I'm thinking the "TAX SLAVE" mantra may be a way of communicating the concept.