I'm not saying taxation is slavery. I'm saying that you cannot have a system in which a portion of the population does zero work and receives resources for free

I'm not saying taxation is slavery. I'm saying that you cannot have a system in which a portion of the population does zero work and receives resources for free without requiring that the other portion to do the work producing those resources. If the productive portion simply stopped working, or only worked enough to barely survive themselves, the nonproductive portion of the population would perish unless they enslaved the productive portion and forced them to produce surpluses.