There are a lot of groups of people who can't take care of themselves: Children, the elderly, the sick or otherwise impaired, indigent, etc. We need to allocate some of the surplus product to take care of them (whether that's called taxes or anything else). This is why even under socialism, there is still a surplus; workers (at least on an individual level) will not keep all the value they produce, because some of it needs to go to these groups (as well as a few other things).

Unfortunately under capitalism, that surplus is mostly not allocated to the groups above; most of it is going to a few wealthy parasites living in opulence, laughing at the poverty of the rest of us.

They're falling prey to a common right-wing talking point: "Its not us who are the parasites, its actually poor people (or mothers or whatever group they want to demonize that given week). Please blame these other groups, its not us!"