I said "payroll taxes are a FORM" of slavery. (along with being a form of theft). Just because we have been doing it and you are used to it doesn't negate this.
If one WERE to compare payroll taxes and slavery, I would say the common element is involuntary appropriation of the fruits of labor. So they are not "nothing" alike. They do share at least one very strong common trait.
If you find the phrase "slavery" inflammatory or "ridiculous" as you put it... fine. I think you are wrong, but it's irrelevant to the larger point I was making anyway.
And that point is... it is better to tax resource usage than to tax labor for a number of reasons. Justice being a primary one, and conservation and improved productivity being others. I'd love to hear your opinion on the actual point being raised if you have one.