Most Christian churches, at some point in almost any Sunday service, will have the congregation recite the Apostle's Creed, or something similar, in which they proclaim, in unison, a summary of what they are expected to believe as members of that congregation. They'll say, "I believe in God the father almighty, maker of heaven and Earth, and in Jesus Christ...who was conceived by the Virgin Mary...etc".
And the way a person becomes a Muslim is by reciting the Shahada, in which they say, "I testify that there is no god but Allah, and Muhammad is the Messenger of Allah."
Belief is absolutely a fundamental piece of religion. Conventions and practices follow from the beliefs, but the beliefs are really where it all starts.
I haven't called for thought policing, but since you bring it up, it's worth pointing out that we do, in western society, expect and accept a great deal of what we might call "standardizing" practices, when it comes to establishing approved thought patterns.
For example, we send our children to schools, and give them failing grades if they don't write sentences with the "correct" grammar, or produce the correct answers on their history and science tests. And we further standardize when we make them pass the SAT, ACT, GRE, LSAT, etc., when applying to higher education.
It can be tricky to find the right things that a society can collectively agree on should be "common" knowledge, but there does have to be some common knowledge.
And the problem with a complete "freedom of religion", is that a religious belief can be literally anything, like a belief in human sacrifice, or a belief that your "God" wants you to establish a theocracy at all costs. And obviously those beliefs can't coexist within a society that generally values freedom of thought. Which is why a complete "freedom of religion" is simply paradoxical.
That's why it's much better to say explicitly what you do and don't allow, as I've suggested:
"Freedom to do and think in whatever makes sense to you in your pursuit of happiness, as long as it doesn't conflict with other peoples' right to the same." Or something along those lines.
A total "freedom of religion" causes pure chaos and capricious rulings of which beliefs get special treatment as "religious" beliefs. But a simple allowance of "all beliefs and actions, except insofar as they impose upon other's right to the same" - that is what we need. And we need to get serious about recognizing that.
The "freedom of religion", as it currently exists, isn't actually protecting anyone from discrimination any more than my proposed wording would. But what it does do is give some people special treatment if they can dupe the rest of us into thinking their beliefs are more "religious", and more worthy of protection than ours.
