If you find yourself not agreeing with what was said or discussed, you are very well in your rights to have a different opinion and even voicing it out, respectfully of course. The problem is that most people tend to not have one and they are afraid that having it will lead them to trouble. Of course, having a differing opinion is not always celebrated, usually with those who are insecure and unsure of themselves, but that does not mean that you should silence your own thoughts and ultimately, self. Be certain of your position and be smart about it. If you know that facing the situation head on would bring an avalanche of repercussions, then find a way to go around it. Start with engaging on a common ground. Establish trust and rapport. But if all is well on that front, then go ahead and rock the boat.