Here’s the breakdown:
Tom is a house cat. He’s supposed to be there. Jerry, a pesky rodent, is not.
90% of the battles are initiated by Jerry. Even if they were initiated by Tom, it’s justified because he’s pretty much fulfilling one of his purposes as a housecat.
Tom has a conscience. In one episode, he threw Jerry and either Nibbles or that little duck outside in a horrible storm, and locked them out of the house. He was so troubled and overcome with guilt from being so cruel, he went out to search for them and bring them back to shelter and safety. Jerry and Nibbles once stole food from a banquet Tom was supposed to be guarding, effectively getting him executed at the guillotine. They didn’t care either, they just ate their food and sauntered away knowing full well they just got a guard killed. On top of that, Tom has even rescued Jerry from certain doom at the hands of other foreign foes.
Jerry has taken advantage of the kindness of Spike, the bulldog that makes appearances occasionally. Spike, based on his own observations, sees Jerry to be an innocent mouse ritualistically tormented by Tom, so he defends him from Tom on some basis. Jerry has hit Spike with a golf club, repeatedly endangered/harmed him and his son, and framed Tom for all those misdeeds. This is how Jerry treats someone who defends him against Tom.
Fuck Jerry.
 "SubblyXatu")