As a minor, anger is pretty much the only way I have of creating negative incentives for my parents that doesn't automatically lead to me being punished, because anger is not seen as purposeful retaliation in the same way that other things that annoy people are. (I can't fine my parents, I can't refuse to associate with them, and I can't damage their reputation within the community without breaking community social norms.)

Anger is also really great for signaling that you consider someone else's behavior extremely unpleasant. If I just tell people I'm upset, I have strong incentives to make this statement when I am only mildly annoyed, and so people can't trust me to verbally signal the level of disutility their action causes me. However, because people generally don't enjoy being angry, you can generally tell that if someone is angry, they are very upset.

Also, my judgement is definitely affected by anger, but I can limit what angry!ilzolende decides to do, because I am aware of my poor judgement when I'm angry, so I default to the the hard rules that my non-angry self sets, such as "don't cause property damage or injury while angry, you're probably wrong". Things I have done while angry:

• Turn on lots of lights and faucets to increase my parents' utility bills, because I thought there needed to be a financial disincentive to their actions. (Unfortunately, losing ~$0.5 at most is really not a strong incentive.)
• Move objects to annoying locations, because I wanted to inconvenience the person who I was upset at.
• Encrypt my hard drive and backup drive, because I realized after catching my parents wiretapping me that the only reliable privacy boundaries were the ones that I could enforce, and trust had just been shown not to work as an enforcement mechanism. This was probably the best decision I've made while upset.