Conscription is literally slavery. Taxation isn't slavery its an obligation to pay a fraction of what you earn ergo if you earn nothing you owe nothing and have no obligation.
Afterthought. I just remembered that some of the more radical leftists call working for a salary a wage slavery, which is similarly silly.
To be a slave is to have your personal freedoms subordinated to another while people always enjoy a finite degree of autonomy which varies substantially from society to society and even between different socioeconomic groups if your owner can tell you where to go and whom to kill, and in fact to surrender ones life if asked then I cannot discern the difference between that state and slavery.