How can you expect someone to be quiet or never mention their religion or faith, when at times...?

...a conversation relating to their faith is being discussed, or a topic that will effect their faith is being discussed? So others can discuss your religion and faith; and how it affects society and yet if you are a believer or follower in that faith you must be silent? Or is that a person can speak of their faith, but only as if they are not apart of it. As if they have no invested interest in that belief. To somehow vain disinterest and connection to appease the rest.