> Those who don't believe in anything at all are atheists.

We atheists believe things. We just don't believe in gods.

You can find spiritual atheists and superstitious atheists and atheists who are flat earthers. All manner of nonsense. But they don't believe in gods.

Some people use "nihilism" to mean belief in nothing, but there are self-proclaimed nihilists who are offended at that.

Also

antitheist

a person opposed to belief in god or gods.

In this day and age many atheists feel the need to be antitheist.

Do they? I haven't run into this attitude organically outside of HN in years at this point. I mean a new cohort of 15-year-olds is always discovering richard dawkins. But the most ferocious organized online atheists seem to have realized they share a lot of values with the new far right and reached a sort of quiet compromise about the religion thing.