Here's what I've learned lately about "telling it like it is": It has to be a natural part of your personality to want to reveal the truth as you see it, regardless of what others may think, and you have to have done it for a very long time. If these conditions are not in place, as they have not been for me, then the second you reveal what you really think, you come across as just-plain-mean.
Some people in work or social situations can just pull off truth-telling better than others. When they do it, it makes them strong, independent, intelligent. When others, like me, do it, it makes them over-emotional, immature, resistant to change.
I suppose when you hold your tongue for the better part of your life, once you decide to not be silent, to not be quiet anymore, it's more than just the situation at hand you are railing against. It's years of bottled up opinions being unleashed on one or two people. When this happens, you don't get promotions at work, and you always feel on the outside in other contexts, because people decide you are not being the nice guy anymore, and they don't want to have such volatility swirling around them. The decision then becomes, do you retreat back to keeping your thoughts to yourself, or do you just try to become more practiced at speaking your mind. That is the question.