Yep. Taxes, by definition, are theft. Who steals my money steals the fruits of my labor, and by extension, my time, skills, and life. Furthermore, they assert (under threat of violence) that they have an a priori claim to those resources that takes precedent over my own.
We can CONSENT to some level of taxation -- agree via social contract to give up some portion of our lives for the good of the Collective. But when government leave us no choice, when it coerces money from us at the point of a gun, then yes, it is involuntary servitude and tyranny at its worst.
But isn't a constitutional amendment the very mechanism of consent you describe?