Holding an opinion which is in fact correct, without being able to give a reason for it, is neither true knowledge nor ignorance
You've heard the remark "Even a stopped clock is right twice a day." To those suffering from ignorance it is a comforting thought. There is no crime in trying to be right without the basic knowledge and even though one misses the mark most of the time at least to aim at it is worthy.
But some people simply play lottery with knowledge, taking for granted that something is true because one heard it somewhere or because one thinks of it oneself. People will aggressively hold on to and defend an opinion for many reasons. One of them is so they won't appear stupid. There are those who will ridicule you if you don't know the answer to something. I used to get that treatment a lot when I was growing up. It took me most of my life to accept the idea that "I don't know" is a legitimate answer to something. It seemed to me there was no compassion for ignorance anywhere in the world.
Having incorrect facts is another reason for holding an opinion. One's opinion may be correct but it's based on wrong information. You take the right road for all the wrong reasons but you get there anyway.
Another type of opinion defender has nothing to do with reasons or knowledge of the facts. It's based on a hunch, intuition, a gut reaction. Someone expresses an opinion as if it was a fact. When you ask him why he thins tht way he will say "I don't know. I just think it's right." If it turns out that he has one of those stopped clock times, he will be trusting his own guts instead of the truth of things.
Given the reasons for opinion building as stated above and many others, the worst kind of opinion not based on knowledge is the opinion we might have of another person. We re frequently put in a position of having to make a value judgment about someone else for some reason. Maybe we are interviewing them for a job, or deciding if we want to see them socially, or if we want to buy something from them or sell it to them. Without living someone else's life we can't possible know everything we need to know about them to make the correct assessment. So it is very important how we frame an opinion about that person and we must avoid doing it superficially by the way they look or the sound of their voice. I've served on juries and it was usually very difficult to figure out who was lying and who was telling the truth. I pity the poor judge who has to do that day in and day out.
Thee is an ocean of difference between ignorance and stupidity. Ignorance is curable.
DB - The Vagabond