People rarely get attacked for an opinion when they make it clear it's just an opinion. The problem is, people pose their opionions as facts, and way too often.
There's a difference between saying "Derrick Green is a Michigan lean" and "Based on his recent tweets, I bet Derrick Green is a Michigan lean." Too many people say the first, when they really mean the second. You won't get attached for the second statement. People might reply with a counter argument, or ask you to tell why you think that, but they aren't going to attack you.