You sound very insecure about age and being mature.
But booing is disrespectful, you could at least not shout anything or clap a bit, so you show the enemy team that you respect them. Then you can shout, cheer and scream from the deepest pits of your soul for the home team. You don't have to boo them.
If you don't understand the basic concept of respect, then, I'm sorry, you are a fucking animal.
I DO NOT ask for cheering for the enemy team, at least respect them.