While the concept of not becoming angry is appealing (and possibly even desirable to some), anyone actively practicing yoga is a human being, and anger is a natural human emotion. We all get furious, including the yogis. Most spiritual systems also encourage us to be present with what is, although "what is" can include a lot of anger. The difference is that yogis recognize their anger and take conscious action to move away from it. When we talk about the yogis being free from anger, they don't mean that they aren't capable of getting angry. They just train themselves to handle that energy more constructively. Instead of letting it consume them, they learn how to release it slowly so that it doesn't build up into a larger rage. In addition, because yoga is an exercise system designed to strengthen the body and mind, it isn't always easy for people to feel happy or peaceful. As you might expect, engaging in intense yoga workouts or long periods of meditation can cause someone who is used to being out among people who trigger them sometimes to want to leave the practice entirely. This is why most teachers will tell you that if you want to truly benefit from yoga, then you have to do it regularly even when you're feeling unhappy or agitated. In conclusion, yes, yogis get angry, but they learn to control that anger so that it doesn't lead them down a destructive path.