Orcs are seen avenging fallen comrades.
Orcs abhor eating orc flesh, and find the accusation that they engage in cannibalism to be an insult.
Shagrat and Gorbag express reasons for following Sauron - one that they fear him, the other that they fear Sauron's enemies even more.
In fact, when you look at what orcs say, it turns out that they have morality rather like human morality. They have loyalties, likes and dislikes, reasons for what they do, and opinions on what is proper or improper behavior, fairness, and so on.
What we see, though, is that orcs are incredible hypocrites. They have opinions and morals, but are entirely self-centered in their application, and do not engage in self-reflection on their own behavior.
This is entirely intentional on Tolkien's part, because to him, this is pretty basic evil that we all see day-to-day, among real-world humans. For, while he placed the orcs in his works all on one side of the conflict, he thought, in fact:
"Yes, I think the orcs as real a creation as anything in 'realistic' fiction ... only in real life they are on both sides, of course. For 'romance' has grown out of 'allegory', and its wars are still derived from the 'inner war' of allegory in which good is on one side and various modes of badness on the other. In real (exterior) life men are on both sides: which means a motley alliance of orcs, beasts, demons, plain naturally honest men, and angels."
-Tolkien, in a letter to his son Christopher during WWII.
So, orcs are people. They're just really crummy people.