Yes, I’ve seen many of them in real life, as well as on internet forums. Even though these people may seem successful and content on the surface, many of them feel insecure, belittled or lonely. Others are …well, let’s just call them not very deep thinkers 
Try asking yourself why do your friend and relative have a constant urge to prove their superiority to everyone, and your annoyance with them will quickly turn into pity.
I disagree with all of the comments that day things like “you may be right” I have a relative like this and another who responds to her that way. Rolling over to keep the peace just encourages them to continue. She quit treating me that way when I looked her in the eye and said I was through discussing whatever it was she was harping about. And I meant it. If she wanted to have a relationship with me it was going to be an adult one where I had equal footing. It took a while, and I had to be consistent like you are when dealing with toddlers, but it’s been several years and we get along great.
I’m not one to easily give up people in my life. Especially friends I’ve had for a long time. Am I annoyed sometimes by their personality traits. Of concourse I am, and they are probably annoyed by some of my personality traits. I accept people for who they are (then I vent about them at home to my husband )
@amandakayak I’m a huge fan of “Bless your heart!”
MIL was a condescending KIA. DH and I suspect/fear narcissism had a large role in the dynamic. We went through all sorts of phases: trying to explain so she’d understand, trying to agree to disagree, then trying to change the subject so she’d back off, Finally we stopped sharing huge parts of our lives with her. We were able to function cordially on a superficial level. It was sad but at the same time heartening that we maintained any sort of contact; all her other relatives had cut ties with her.
Was in a conversation with an (insecure) overbearing person I expect never to see again. When she pronounced “Well, you’ve got to [do such-and-such],” I tilted my head and said, “No” and let it hang there. She back-pedaled to fill the airwaves. YMMV.
@bhs1978, I stuck with this person for 15 or more years. I would prefer not to “give up” on the relationship, but there is a bit more to the story. The latest “Know-It-All” response came in an email responding to my invitation to coffee with the idea of sharing some material she would be interested in. She didn’t respond to the invitation, just proceeded to tell me how my approach to our shared interest is wrong. I’m not surprised to be told that I am wrong, but seeing this in writing with no regard to the invitation to a shared get-together is more than I can take at present. Perhaps I’m responding as an adolescent would when “friends” ignore a party invitation, but I am rather hurt and will be taking a break.
My eldest sister “remembers” it all. She’s quite a bit older - 16 years - and I’m wondering if dementia may be looming. She recently mentioned how well she remembers my rehearsal dinner - at a place and location both wrong. I corrected her, saying she must be thinking of someone else. Nope, she insisted it was mine with no doubt that she was correct and I was wrong. I dropped it but mentioned it to my husband later. He confirmed I wasn’t forgetting my own rehearsal dinner. She does this a lot lately. She insisted I didn’t have a cat when I was little - she would have remembered. (I did - his name was Chocolate.) She told me the name of a cat I had after I married and got it wrong. When corrected - well, she can’t be corrected. It makes talking with her difficult. And yeah she knows it all too, which I find less frustrating than when she “remembers” it all.
@ignatius, I can relate to that one, too! My relative “remembers” and the memories provide a good reason for her to know better than me. It does make conversation difficult - no possibility of a meeting of the minds or shared exchange. I find it very sad also, seeing the aging.
I think that people in the early stages of dementia dig their heels in about their version of family memories out of fear. That’s different than having a relative or friend who tells you what you feel or think, or who tells you what your words meant. My relative was like a bull dog – literally in your face until you backed down and agreed that she was right whether you actually believed it or not – and I wasn’t prepared to pass on that pattern of behavior down to our children.
Not excusing the behavior but are the know it alls, older and or a person who doesn’t have a lot of outside contact?.
I’ve found that people who for whatever reason, don’t interact with other people as often become much more combative. And even if they do interact with others as they age, become more opinionated and argumentative.
My mom, since my dad passed away, seems to want to argue with me for no reason. She doesn’t even disagree with me, just wants to argue. Also, she will say something about a plan we might have. . I will answer her, with a definitive answer. She only hears her question and her answer and dismiss that I said anything. And be upset that I am not exactly following her plan.
I find the same thing happens with younger people, but mostly those who very rarely get out.
An older gentleman in my extended family insisted at dinner that Oberlin had gone out of business. There was an Oberlin graduate at the table in addition to a college counselor. We gently suggested that maybe he was thinking of College X or College Y? Nope, it was Oberlin! Definitely! He’d read all about it just a few weeks ago!
Okay then…
Although I don’t like electronics at the dinner table, that’s when someone needs to whip out their cell phone and settle the discussion. 
Sometimes it really doesn’t matter what the correct answer is, and things are better left as the person suggests (when things like dementia are involved).
I had a relative that insisted only she knew when my birthday and her H’s birthdates were (she jumbled them and assigned me her H’s birthdate and him mine). She swore we didn’t know our own birthdates for several years—it was very weird.
^^^That’s beyond weird.
Yup, I was pretty astounded but her H went along with it, so I just ducked and waited until she finally realized she had switched our birthdates. In the meantime, she even threw her H a surprise Bday party on my bday, which was a great surprise since it was 7 days prior to his actual bday.
^^^^^ And I thought I got confused over dates… Thanks for the laugh!