VERY aggressive with men

Our male neutered cat is 2, and so aggressive with men with the exception of his owner. We got him as a kitten and he was fine for the first 6 months or so but it's got to the point where we're afraid to have guests over. When we do we normally have to lock him in the room. He attacks visitors, scratching and biting them. He makes the most horrific noises, and hisses/spits. He's usually a dream with me and my spouse. Any ideas on what we can do? We've tried a number of things. talking to him calmly, stroking him. Distracting him with toys. We need help. Thanks!

Your boy is very territorial and protective of you and your spouse. It's not uncommon. Keeping him away from visitors in a separate room is best. 

The part I find strange is its JUST with men. And any of our male friends that visit, visit often, and he just seems to be getting worse. You would think that Over time he might get better or used to visitors but the opposite is happening.