Inter should have considered why they should let themselves lose and let Monza get the win in this match. Maybe if they let another team win in that match, it would be easier for them to get extra points. Monza only got 1 win in five matches in a row, and this made them distrustful because they managed to win against Inter.
Yes, that's how it should be. Inter's main goal should be to win every game and achieve as many wins as possible. If they let other teams win in certain matches, only to get additional points later, this could risk inter milan being in danger of failing to finish in the top 4 this season. Winning over Benfica in the UCL, perhaps a fortune for Inzaghi, but his tactics in A-Series are dilapidated (losing continuously).
Every Inter Milan game has to be taken seriously and every team has to try to win the game with their best efforts. Monza's win against Inter could just as well show that Monza have shown their best game on the pitch and deserve to win the game.