presumption

Mom: If you knew anything about history, you wouldn't vote for him.
A.: Bye, mom. I don't have time for this.
Mom: You don't know history!
A.: Bye, mom.

As a general rule, when you're interested of convincing someone rather than insulting him or her, don't insult them. Mom's not the only one who doesn't see how that work; I recall a recruiter from Medecins Sans Frontieres (as known, in the humanitarian aid community for its sanctimony and stubbornness as for its great work) telling an audience of grad students interested in aid work that they have no idea how lucky they are or what kind of hardship exists in the world. I could go on and on with examples.

It's not just the presumption and insult that detracts from the message; it's the arrogance of telling someone else what they know/think/don't know/don't understand. I can't speak for everybody, but I know that once someone starts lecturing me about what I don't know or understand, I become, if anything, less open to what that person has to say. When you respect someone-- a family member, friend, other person you're talking to-- you don't conduct a discussion under the assumption that you know better and just need your colocuteur to see the light. It just doesn't work that way.

***
A few minutes before mom opted to end our conversation on a condescending note, I'd asked my parents why they couldn't be bothered to set up frequent flier accounts with the airline. It can't hurt in any case, but I had good reason for thinking that mom valued frequent flier miles, as she'd mentioned several times in the past that I could give her mine. I sort of figure that since she'd ask, she would actually care enough to claim her own miles. What was I thinking? Anyway, then she asked me to set up accounts for her and dad, because it's not like she's the one who's retired or anything. And besides, now that I think about it, I think they have accounts and have lost their information... which puts me in the happy position of not being able to deal with it.