The phrase "freedom of religion", is self explanatory. It’s the “free exercise clause” of the 1st Amendment. Practice whatever mindless theology you like as long as its precepts do not violate the laws of the land (i.e. no human sacrifice, no animal cruelty, no polygamy, etc.)
But we also have the freedom not to have a religion and to reject belief in the supernatural. According to Article VI, Section 3 of the US Constitution there can be no “religious test” to hold public office. Thus, since only citizens can hold public office, a lack of belief in God is a guaranteed right. The six states whose constitutions still require belief in a supreme being to hold state office have been deemed unconstitutional by the US Supreme Court.
So, when G. Bush Snr. declared that atheists are “not patriots and possibly not even Americans”, he rejected the Constitutional protection under Article VI, and demonstrated the depth of ignorance that gave birth to his son’s mental frailties.
Along with the freedom from having to have religion, we also have the freedom / the right to expect that public schools, publicly funded facilities are free of religious teaching, religious symbolism, and religious proselytizing. This is where the “Establishment Clause” of the 1st Amendment comes into play; that “Wall of separation” phrase that Jefferson coined, that Madison and others echoed.
We have the right to expect that the military services, public symbols, and government agencies are nonsectarian, non-proselytizing, religion neutral, and respectful of the rights of non-believers not to believe.
Finally, we have the right to expect that we be free from the government passing laws that impart favoritism on any religion; free from their spending our tax dollars on religious institutions; free from government promotion of religiosity. It’s these points where things tend to get messed with and ignored thanks to religious fanatics in government and their fundie supporters, largely due to their lack of familiarization with the writings of our Founding Fathers and Supreme Court rulings.
But, theists are correct that my freedom from religion is not absolute. “Freedom from religion” doesn't infer I have the right to expect that I be free from the intrusion of having to see privately funded religious billboards, hear a street preacher, or see crosses on churches; nor should I expect to be freed from having to hear politicians invoke their deity’s name, or follow their religious precepts when voting on bills, or appealing to their constituency. That’s the right of free speech and the freedom of religion.
In short, a theist’s right to Freedom of Religion stops when they try to directly impose their fantasy on me without my expressed consent, or when Freedom From government sponsored Religion, in violation of the Constitution, begins.
Everything else relating to the foolishness and ignorance of theist thought and practice is their problem, and their right. There is no law against self delusion or stupidity