The world is dominated by Nobility Clans who think commoners without a bloodline are barely human. The MC is someone without a bloodline. You can't expect the MC to bow his head to them right? They dominate everything so if he wants a place in this world he has to clash against them. But he can't go all out and have them as mortal ennemies while he isn't strong enough. The world has still some sort of rules so the MC uses them to be safe. If he pushes too far his ennemies will disregard rules and just kill him. But don't worry when he has to be ruthless he can be.