That's why we have laws which define the boundaries and interactions between the freedoms of society's members. It's not useful or practical to define freedom in any other context (i.e., that in nature, outside of society), because there would be no conflicts in that case. Freedom can only really be discussed in terms of social relations.
But these are issues that U.S. courts have had quite a lot to say about: http://en.wikipedia.org/wiki/Freedom_of_religion_in_the_Unit...
And the situation with Islam today certainly has historical precedents:
Anti-Catholicism was widespread in the 1920s; anti-Catholics, including the Ku Klux Klan, believed that Catholicism was incompatible with democracy and that parochial schools encouraged separatism and kept Catholics from becoming loyal Americans. The Catholics responded to such prejudices by repeatedly asserting their rights as American citizens and by arguing that they, not the nativists (anti-Catholics), were true patriots since they believed in the right to freedom of religion.
I agree, it was unreasonable of the security guard to do that. However, if the Muslim religion is violent when taken seriously, it can be valid to question whether someone is a believer in that violence.
What I should have done is left to question whether the Muslim religion is violent when taken seriously, because I'm not sure about that.
Do you agree with the if-then clause in my argument?
When you say freedom of religion, you don't mean complete freedom. What if my religion states that I shouldn't pay taxes? Obviously this religion would not be tolerated.