The midfielder found himself on the receiving end of a stamp from Newcastle United skipper Jonjo Shelvey with the scoreline goalless just after the break, an incident that led to the former Liverpool man receiving his marching orders.
"He was calm - that's important," Pochettino told Sky Sports News. "Last season, we talked a lot about that, how we need to behave and improve and learn.
"He's mature enough now to accept sometimes what happens on the pitch, but he is so calm, he is so brave. Then he scored - a great goal - and I am very pleased.
"I think it was clear it was a red card. The referee has seen the action, it was very clear. It's unlucky for Newcastle. I'm sure Rafa is upset about the situation. Sometimes when you're a player on the pitch it's not easy to have the control."
Alli has now scored eight goals and registered five assists in his side's last 14 league games.