Sometimes called "strong opinions, weakly held".
I find this principle to be incoherent - if you understand something well enough to have a strong opinion, you understand it well enough to hold that opinion strongly. Holding strong opinions on things you don't understand that well seems unhelpful.
As a poor example, my mother has fully bought into a snake-oil scheme where they sell you concentrated hydrogen peroxide as a cure-all. She won't hear a word against it, she always brings the conversation back to "OTC hydrogen peroxide has stabilizers in it." Asking "what is a stabilizer" gets no response.
The truth is, she doesn't know what a stabilizer is, but it's plausible enough to her that they could be "bad" that she's willing to buy the rest of the farm, along with the cow.
How can you argue against that kind of strongly held opinion? When the other party won't listen because of how strongly held the opinion is, you might as well talk to a wall.
[1] http://www.h2o2.com/technical-library/default.aspx?pid=76&
Up against a dishonest debater, this is exploitable to lessen your influence, even if your position is relatively stronger, against (unsubstantiated) claims of being an expert.
"ball_of_lint claims to be uninformed and doesn't have an opinion. That's okay, listen to me, I'm an expert"
If someone strongly claims they know something and I later find out that they were wrong, I simply can't trust that person ever again.
I'm glad you're a critical enough thinker to do that (although it's unfortunate that you don't account for honest conviction or that person obtaining further understanding such that they change their position; after all, not all strong claims revealed to be wrong are meant to deceive). Not everyone is that kind of critical thinker, especially up against a savvy, dishonest debater/character/charlatan. Some people just keep shouting "I know the answer" or "Believe me!" to every question or issue and they end up with a following.
That's one way of thinking, but I reject it. You'll easily be manipulated by political and corporate agendas if you think this way.
Often my own intuition is at odds with the "evidence I have" and I turn out to be right later. If I had jumped to the (extreme) conclusion that smoking was healthy back in the 70s and 80s because of the evidence big tobacco was pushing from the shadows (doctors recommending brands, etc) I might not be here today.
Often my own intuition is at odds with the "evidence I have" and I turn out to be right later.
I mean evidence in a broad sense, encompassing all information available to you for basing your worldview upon, including your intuition. If your intuition has been reliable in the past, and the scientific evidence was being put out by entities with obvious incentives for a certain conclusion, then it's rational to weigh your intuition highly relative to the scientific evidence.
I think the people who are against forming strong opinions on little data, thinks it essentially means being confident, speaking your mind, and influencing others towards seeing things your way, when you haven't done much research into a topic. Which I think is a bad idea, because it has a high chance of propagating misinformation.
Let's take the example of where someone yells "Duck!". Most likely, you weren't paying attention and you have no clue why they would yell such a thing. There is a high chance that it's some kind of prank. But, I argue, you should still duck anyway, because the potential benefits (not getting a concussion) outweigh the risks (looking stupid).
Similarly, if you are running a startup, you should prepared to pivot at the first sign of customer mismatch, but meanwhile the majority of work will be in one direction, and you should work on it passionately.
So by understanding something you dislike well, you need to appreciate its pros, which will lead to a weaker negative opinion about it. Conversely, understanding something you like well, means you need to come to terms with its cons as well, which should lead to moderation as well.