Yes, here you're right. There is a ref mistake and a "ref mistake".
Ronaldinho's goal against Inter was scored after offside, but Kaka was almost on line with the Inter player. The picture didn't froze, players go from onside to offside in 0.0001 sec., and these errors are normal human errors. The same could be said about Gila's goal against us that was given offside, and even about Adriano's handball against Milan that no-one except for Abbiatti saw when it happened (we needed the replays to see that it was handball and we even needed the right angle).
But there are situations where the refs must not make a mistake. Maicon's goal against Siena wasn't a normal mistake, neither was the penalty given to Balotelli. On the other hand, the ref was right next to Marchionni when Marco was 1 meter offside before he assisted Del Piero vs Atalanta, and the ref was next to Marchionni when he stopped one attack with his hand against Catania.
Milan were helped even more than we and Inter. The penalties they were given at the start were scandalous.
Also, there is a lot of talk that Inter didn't concede a penalty for a year. Obviously, they are still to concede a penalty this season in serie A.
But are we the right ones to object about this? We conceded only one penalty this year and it was in the last minute, against Genoa, on a match we were already winning 3:0.
We got 4 penalties in our favor, Inter got only 2 , Milan got 8.
We got 2 red cards, Inter got 4 red cards.
It's not so one-sided as one might think. Without counting the first 7-8 rounds when Milan were getting an obvious, and perhaps intentional help, the rest of the season is more or less equal with the big teams getting almost equal number of calls against or in their favor.