A defining trait among the military community is the ability to completely insult someone one minute and drink with them the next.
Troops can get down right heartless by civilian standards. But what keeps troops and veterans from being just pure assholes is that no one is mocking their brother out of hate. It's just part of the culture — besides, our buddies are firing their own shots right back.
The stereotypes are usually that Marines are dumb, airmen are primadonnas, soldiers are fat and lazy, sailors are gay, and Coasties don't actually exist. Obviously, these aren't 100% true. They're jokes even if you have come across a handful dumb Marines or fat soldiers.
Want to know what happens to a civilian if they jump in and call Marines dumb? Ask that former teacher in Pico Rivera, California.
You'll see some outright "hatred" for the other branches, especially when it comes to our Academies playing each other in football. If your service loses the game, your entire formation is screaming, "Oh man! F*ck the [other branch]! At least we don't focus on playing some stupid game!"
And that's at it's most savage. Generally, it's kept at "Go Army, beat Navy!" and vice-versa. An attack on one branch by an outsider is treated as an attack on all branches.
Deeply personal jabs
If you've spent nearly every waking second with the same people for god knows how long, you learn every detail about their personal life. Nothing remains a secret and nothing stays off-limits.
What better cure is there for a terrible personal tragedy, like an unfaithful spouse, than having your best bros mock you for crying?
Expletive-filled (yet creative) rants
Expletives in conversation are like adding a bit of spice to a meal. It's how you add some extra "uhmph" to a statement. "I don't like you" has far less sting than "f*ck you" and it's a sure way to get your point across to most people. Except vets and troops.
Obscenities lose their magic after you've been desensitized to them throughout you're entire career. Telling your peer to "eat sh*t" just becomes a substitute for "hello!"
Politically incorrect jokes
Once you've spent years in training, months in combat, and nearly a life time of brotherhood with someone, it's only then can troops tell a joke to each other that would shock the average civilian.
The only reason these kinds of (crass, insensitive, and hilarious) jokes are kept between the two is because there isn't a shred of hatred in there. Not saying it's right or even justifiable — only saying that if it's between two people who've been to hell and back, it's meant with the best of intentions. After what we've seen, gallows humor is the perfect coping mechanism.