True, yet they often do not realize it. It's also why authortarian governments do not like independent religion.

This is a little concerning to me. I see religion and the state as opposing forces for change. I wish we had more diversity in how atheists could organize outside of religion.

That’s awful. There is nothing voluntary about giving to the state nor is there any selection in what cause to support. Pretty antithetical to charity.

Why do you think charity needs to be voluntary and give you the option to be discriminatory? It sounds like your idea of charity centers more on making the donor feel good about their choices than on actually helping people most in need. If taxpayer-funded programs can do a better job of helping people than religiously-motivated charities, then your concerns about whether it's voluntary are antithetical to the end goal of helping people.

There's another word for being "charitable" with other people's property, and that word is "theft".