He had a bottle of whiskey and he drank that. (1.14)
Yep, the whole bottle. Mattie wants the readers to understand that Tom Chaney's drunkenness led directly to his murdering her father. We get it.
"[…] You see what I have come to because of drink. I killed my best friend in a trifling quarrel over a pocketknife. I was drunk and it could just as easily have been my brother. If I had received good instructions as a child I would be with my family today and at peace with my neighbors." (2.14)
Here, Mattie's recalling the speech of a man who's about to die. He blames alcohol not only for his murder of his friend, but to his own about-to-be-hanged state. Notice that the man believes that abuse of alcohol is a result of a bad upbringing. Today we know that alcohol abuse has a lot to do with brain chemistry—but it can still lead to terrible consequences.
"The meanest on is Rooster Cogburn. He is a pitiless man, double-tough, and fear don't enter into his thinking. He loves to pull cork. […]"
"Where can I find this Rooster?" (2.37-38)
Apparently, it's perfectly acceptable for U.S. Marshals to drink on the job. Great! That probably doesn't lead to excess force at all.
"I would not put a thief in my mouth to steal my brains." (3.314)
Ha. We're so stealing this one next time someone offers us a beer at a party. (No underage drinking, Shmoopers.) Mattie doesn't have any positive associations with alcohol; we bet she never drinks a drop in her life.
"I have a writ here that says for you to stop eating Chen Lee's corn meal forthwith. It is a writ for a rat and this is lawful service of said writ." (3.330)
Rooster is both funny and scary when he's drunk. We really don't like the idea of this guy with loaded weapons, and not just because we don't want to see any more rats get shot.
I have never wasted any time encouraging drunkards or show-offs. (3.330)
Mattie's approach to Rooster's drinking is no-nonsense and blunt, just like her approach to the rest of life. Encourage? No. Tolerate? Yes—for just as long as she needs to, to get the job done.
I suspect now that [Dr. Underwood's Bile Activator] it made use of some such ingredients as codeine or laudanum. I can remember when half the old ladies in the country were "dopeheads."
Thank God for the Harrison Narcotics Law. (4.2-3)
Uh, yeah. Before the Harrison Ant-Narcotics Act, anybody could buy or sell narcotics. Laudanum is an opiate, the same stuff that they make opium and even heroin out of. They used to give that stuff to babies.
"The man Chaney, the man with the marked face, killed my father. He was a whiskey drinker like you. It led to killing in the end." (6.144)
Just in case you haven't figured it out yet, drinking is bad. Forget Just Say No: they should hand this book out at anti-drug assemblies.
On one long climb he fell off his horse, but he quickly gained his feet and mounted again.
"That was nothing, nothing," said he. "Bo put a wrong foot, that was all. He is tired. This is no grade. I have freighted iron stoves up harder grades than this, and pork as well. (6.525-26)
Uh, well at least drinking and riding is less dangerous than drinking and driving? We guess? Mattie is the type of person who wants to be sharp and alert for everything. Rooster, on the other hand, seem to be trying to forget the pain of his life.