I know what you mean, but I think life is too short to hold in your opinions. In my opinion we should just trust other people not to put too much stock in them and shoot our mouths off. In this small world we inhabit it is too easy to devalue any opinion because someone else has a different one, I think as long as we respect that others have different views and we try our best not to upset anyone we should express away.
No one ever reaches a point where they know enough or know everything, so say what you think but be prepared to humbly revise it later.
Just my 2ps worth!