Religious liberty is a recognition that peaceful people of various faiths or non-faith can live together in the same community and appreciate and honor each other. It does not stifle free speech by prohibiting a person from sharing one's faith with others in a peaceful way, but it also does not allow for religious coercion. It requires a balance.
Sometimes people use the term "religious liberty" to support their ability to stop other people from practicing their faith. That's not what it is about.
There are also some limits on religious freedom when it comes to harming other people. Although one could theoretically volunteer for something as extreme as, say, human sacrifice, and this could theoretically constitute religious freedom, society has limits on what it will allow.
The Universal Declaration of Human Rights (
http://www.un.org/en/documents/udhr/ ) gives some good definition to religious freedom:
Article 18 - "Everyone has the right to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief, and freedom, either alone or in community with others and in public or private, to manifest his religion or belief in teaching, practice, worship and observance."
In general, there are very few places where people can legitimately claim freedom to do something that they deny to others.