You should never be afraid to state your thoughts and opinions for fear you will lose a friend. If you lose a friend over an opinion, belief, or "statement, then that person wasn't really your friend in the first place."
If your opinion on a topic is different than that of your friend, and when the topic is discussed, that friend no longer wants to be friends with you because of how you feel about the topic, the that person was never your friend to begin with. That person was friends with a belief they had about you, and not actually with you yourself. Friends, true friends, accept you no matter what your opinions are, and respect that they are your opinions and your beliefs even if they don't coincide with their own.
This goes for general subjects like politics, religion, news stories, or other things that are general to everyone.
This does not cover, necessarily, a thought or opinion or belief about each other that is grounds for friendship removal, such as one friend believes the other is cheating with their significant other, and will not believe otherwise even if it is not true. Or other opinions about each other whether true or not.