Adults

For someone who runs around boasting about how are 19-years-old and demanding ass kissing and blocking anyone who says something, they do not want to hear... Yeah, that is being mature. 
Most of them can't take criticism and will resort to BAWWWlocking when someone calls them put. However, it is not just on the Internet, adults can act childish and bratty in real life too. 

"I'M 19!! I'M AN ADULT NOW, SO I SHOULD BE TREATED LIKE ONE!!" 
I mean, I'm immature and childish sometimes too. However, I usually act that way on purpose when I'm goofing off and being excited. Not begging for ass-pats because "I'M AN ADULT!!1!!"

With that attitude, we will rather treat you as if you are fucking 2-years-old because that is how you are behaving.
If you want to get treated as an adult, then ACT LIKE ONE! Otherwise, people are going to keep treating you like a little-spoiled child.