Sure you can. However, if your talking is not advancing the cause, and may in fact be harming it, you'll find people on your own side interfering with your right to speak on the subject.
Let's use your analogy for a second. Say you're a German, c1939. Yes, you're against the Holocaust, and you're willing to try and stop it. Do you do your cause any good by attacking the officers who tried to assasinate Hitler because they aren't as philosophically pure as you are about Jews?
That's what happens when good folks allow the perfect to become the enemy of the good.