I'm pretty sure that people below 25 have always been referred as young adults. What else would you call them?

I mean not just the adjective young but qualifications about age related stupidity, immaturity or youthfulness or other cues that soften the narration. People calling me "young man" is not what I needed more of, more about contextualization that one's not doomed and that there's a lot more to come

I don't have a problem with calling them "young," since they are objectively young, but I do have a problem with caling them "youth." One of my coworkers just started a "youth forum," going on to say that it was for people ages 18-25. I advised her that we wouldn't normally call that demographic "youth," that "youth" usually means 13-18 or so, and she looked at me like I had three heads. She's about 25. This weirded me out - until very recently, young adults liked being called young adults and resented being mistaken for "youth." I find it unsettling.

Whenever I am bantering with anyone in their early 20's, and the chance arises, I steal the William Gibson line, "I have a pair of shoes older than you are, so what are you supposed to know?"

Ha, I was talking to my mother on the telephone. She referred to me as "young people like you". While at work I'm the senior authority in my role. And people who are around 25 sometimes can't help themselves and call me sir. (well, actually they use the formal form of the second pronoun. Like vous in french and Sie in German)
So my mother and I agreed that young is a very relative notion.

A couple weeks ago, I called a 35-year-old woman "kid". She laughed.

In our denomination, you're a "young adult" until..... probably 30-35. stynxno is attending the national conference this summer as an official "young adult" delegate from our synod, and he's 30.

YEah, I'd say "young adult" is good until 30 at least, and even in your 30s older people call you young. I still get told I'm young by people in their 70s/80s, even 60s, and compared to them I am. Because I sometimes feel sad about the passing of time, which seems so fast, I am glad to be reminded that life, if you're lucky to get a full 8 decades or so, is long, and that it's by no means all over.

try being a bridge player under the age of 40. I'm 37 and my regular partner is 50 and we still get called "the kids".

Fifty years! A man’s lifetime!
Compared to the span of Heaven
Is but a dream.
What is given life
Must surely die!

My mom's 97. Everyone's young to her.

Generally, people aren't done growing until 25, so technically that is young.
I would like for this to account for the number of people in their early 20s who think their lives are over or irreparably fucked up or etc. as well. If the part of your brain that does long term thinking isn't finished forming, maybe they can't imagine a future, possibly the inverse outcome of common adolescent thinking that they are immortal/invulnerable: if there is only now, I will live forever! If everything sucks now, it will suck forever!
I think youth obsession is possibly worse than ever, so that probably adds to the idea that somehow if you do not have everything exactly perfect by 25, it's over, but, seriously, and even though I am pretty sure a lot of it has to do with my sample groups, this crop of people in their 20s seem shockingly ignorant. I have so many questions.
Like, is pointedly mentioning that you really like sex a reference or an advice trend or a thing for guys I have not heard of? Because is it not a given than guys in their 20s usually really like sex? Is my response suppose to be, "Really? I had no idea! Well, we should have sex right now because you really like it and my job is to please you!" instead of, "If you hadn't said that over and over, I was pretty sure you were asexual, but now I am convinced."
Similarly, if someone keeps mentioning that they really like pie, are they expecting me to go make them a pie? Is there something inappropriate with the "so go get a goddamn pie already" response?

I do not quite understand the use of aggrieved here.

That's a good point about it being like adolescent short term thinking. I was just reading about this 22 year old who shot himself after a breakup (and probably cause of other factors) and I'm like damn; this dude really didn't realize how temporary his feelings are about whatever he was hurting about

I think the total casualization of sex preferences is pretty much the end game with the culture of a million 19 year old sex columnists and the commodification of sexuality in advertising etc. I was watching someone being interviewed on The View and one of the ladies straight asks the guy if he has a foot fetish randomly on mass TV. Talking about sex for some people is like talking about the weather.

The pie thing, I don't know how much this is a "real life" phenomenon but in terms of media and Internet I noticed people used to do this with Bacon a lot. It's strange.

That is young.