There is no magical change that happens on a person’s 21st birthday that makes them suddenly able to handle alcohol. There’s no fundamental difference between a person on the day before their 21st birthday and on the day after.
Now, I know Josh Hutcherson’s 19, that example was just to enforce the point that the strictly-enforced legal distinction between legal drinking and underage drinking is pretty arbitrary, and not based in any kind of science or psychology. An underage person isn’t always being irresponsible by drinking, just as someone over 21 isn’t always doing it responsibly.
In fact, you know who’s generally the least capable of drinking responsibly upon turning 21? The people who never had a drink until they were of legal age. Imagine a police officer who never picked up a gun until it came time to actually use one in the field. He’s going to be a poor shot, he won’t know how to handle one, and he’s likely going to shoot someone other than the person he intended to shoot.
I’m not saying you should go out partying underage every night, that would be stupid and irresponsible of me. Unless Josh is really bad at holding his liquor, chastising a 19-year-old, someone who is legally capable of purchasing cigarettes and pornography, serving in the military, sitting on a jury, and voting, for imbibing alcohol just seems kind of silly.
You should not judge Josh Hutcherson for drinking underage, because in reality, the only thing he’s necessarily done wrong is getting caught. It was a rookie mistake, as an up-and-coming a-lister, to attempt use of a fake ID, but if he hadn’t gotten caught and I found out he drank, I would think absolutely no less of him.
Oh, and unless he’s in jail for filming (unlikely he’ll do much time if any, since he’s a 19-year-old, incredibly rich white guy), this won’t affect his acting, not one bit.