Now don't get this confused with trying to convince someone else of your beliefs or a decision you're unsure of. If you want someone to agree with your opinions, then you will have to explain your reasoning and back it up with the facts that you used. Don't forget to offer counter-points, it's rare that a position is one or the other and no imbetween. Offer all the facts and let the people make their own choices. Hiding the truth means you're scared of it because you're not confidant your choice is the right one. If it trully was, it should be evident based on the facts. As for if you're unsure of something, it's good then to let people know where you're coming from so they can help you in the decision making process. If they feel you're correct in your thinking you'll recieve validation, and if you're wrong then you will have spared yourself at the least some embarrasment.
The original point I was trying to make though is that if you feel you are right, you don't need to explain yourself. Unless you're trying to convince others of your beliefs, it shouldn't matter what they think. You know the truth and that's what's important.