Context
A long time ago I came up with a pithy phrase that a person is like HTML: content and representation mixed in together in one. The practical application being: if you have great stuff to say that's awesome, make sure now how you look doesn't get in your way.
Only very recently I came to realize that an equally important part here plays context.
Imagine you're at a soccer game (why soccer? because I don't know any other sports) and you hear someone yelling “pass it! Pass it on to the left!” - what do you think of the yelling person?
Let's assume the advice is true/correct. Let's assume the person looks the same. But it will go down differently depending on who that person is, what their place is.
If it's a coach - you'll listen, players listen. If it's a member of the team - you'll think it's a sound advice, teammates on the field might feel the same. If the yelling coming from where the press is sitting, it'd be slightly unusual, maybe too passionate? Safe to assume no one will follow it. But the most ignorable yelling comes from the watching fans - which is the majority of people at the stadium.
The practical bit here is: before delivering your opinion, think what your role is in the context. More often than not, the context will be wrong.