The Nerazzurri ran out 6-2 winners at San Siro, opening the scoring through Mauro Icardi after three minutes before Antonio Candreva and Lautaro Martinez each notched braces and Dalbert also found the net.
Wary of the possibility of an upset on Sunday, Spalletti paid tribute to Inter for the way they kept their focus throughout.
"I told [Benevento coach Cristian] Bucchi after the final whistle that he ought to be proud of that performance," Spalletti said on Inter TV.
"When we went 4-0 up, they could have just given up and our attitude, for a few minutes, was that the game was over. But they tried to stay competitive, got stuck into us and tried to win the ball back.
"However, we rose to the challenge and managed to restore our advantage. This was a proper game, a tough one. Credit goes to Benevento for that.
"My players showed themselves very professional in the way they worked during the week. They were ready when called upon.
"There is always a risk of a drop-off in quality in these games. You risk getting shown up and embarrassed. This time I'm happy.
"The players have shown the progress that's been made in terms of consistency. They've gradually learned that you've got to give everything in every game, no matter the opponent."
Bucchi had a similar outlook, adding: "After they took the lead within three minutes from the penalty spot, it all became more difficult. That's why I told the lads to play open and not think about the result.
"We were up against a strong side, both as a team and in terms of individual players. I liked the character we showed at San Siro, creating so many chances and not letting ourselves be demoralised.
"The real difference between us today was in the finishing. We had the same number of scoring opportunities, but Inter scored six goals and we only had two.
"We leave San Siro with regrets, but I am happy with the performance."