Are male dogs less aggressive when you get them fixed

We have a male dog who is somewhat aggressive. If you tell him to get off the bed he’ll growl at you and not listen. We do discipline by correcting his behavior and saying “HEY!” when he growls in a loud tone so he knows it’s not okay. But he’s so big he probably realizes no one can really move him or do anything to him so he feels like he can act however he wants. He can be scary sometimes because all of a sudden you’ll be petting him and he’ll start growling at you. He’s not fixed and my mom says getting him fixed will make him less aggressive is that true?