This question is a loaded - we are allowing others to have their beliefs.

Not allowing theists to wield government institutions to compel, indoctrinate and recruit others into their religion, is not a banning of a belief. It's maintaining a secular society that's open and fair to all, as it was originally envisioned to be, at least within the U.S.

Ironically, atheists in the U.S., alongside other flavors of non-believers, are continually under attack or are slandered by theists. We're constantly having to correct misconceptions from people who were lied to from the pulpit.

Atheists were found to be the most distrusted minority [1]. It's nearly impossible for a known atheist to run any kind of high level office, and succeed. Atheists "coming out of the closet" frequently lose friends, family and sometimes their jobs, by those who were misled into thinking we're evil, untrustworthy and immoral.

Speaking up and standing up for ourselves is for self defense. Websites like this one are a manifestation of that. We have a backlog of 2000 years of uninterrupted slander to process.

Beyond that, allowing people to have their beliefs doesn't mean we cannot try to persuade and educate. Beliefs inform our opinions, such as who we vote into public office. Beliefs matter, and so therefore, it matters that those beliefs are true and accurate.