Because I say so

It can be the other way around as well. Do you know how many teens I've seen that will start shit but when their argument falls apart or they realize they bit off more than they can chew they go " I'm a minor and you're literally harassing me " and sometimes even then continue to stir the pot while acting morally superior because the person they're arguing with is " harassing a minor "

It doesn't stop at 18. Trust me. I've been on both sides. In your early 20's late 20's and up (especially at work) may often dismiss what you say because "everyone thinks that way when they're young and inexperienced." When I was 31 I had a serious heated argument with my former boss who was almost 60 (we'd hang out after work often) and his only reply to my logical statements was: "some day many years from now when you're mature you'll understand my position." Its just something we all have to learn to deal with in life because it really doesn't go away, and someday you'll very likely find yourself guilty of doing the same thing. The funny thing is a lot of the time it's true, we only find out years later. What's annoying is when you were right. Only time will tell though, and by the time you find out it seldom matters anymore.

We have an event at my school every year where the year 7-9s from each house compete against the others in three drama categories and it's run by the sixth formers. But, I'm the oldest in my group, and lemme tell ya, "I'm an adult and I'm in charge" works when 11 year olds are wasting half the limited time you have with unnecessary arguments

Whining "Why?" and "That's not fair." isn't winning an argument.