[Lizavetta]

but pointed out that it is illegal to “charge an atheist more than a Christian."

Why isn't it illegal to charge a non-senior more than a senior?

[Boogieman]

Because seniors (actually those 40 and over) are a protected class under the federal law, but younger people are not. So, you could charge seniors less than younger people, but if you tried to charge younger people less than seniors, that violates the law.