Marking His Territory

My 1y/o Chi/Min Pin mix (lovingly named Patrick "Onyx" Starr - Patrick Starr because he is silly like Patrick from Spongebob and Onyx for his deep, shiny, black fur) is beginning to mark up my mother's house. For the first time the other day he lifted his leg and began peeing on the leg of the coffee table while looking me in the eye. I didn't see him initially, but when I did I chased him down and rubbed his nose in it while giving him 2 firm taps on his backside. Then, I put him in his time-out crate for 30 minutes. He hasn't marked that spot anymore but he always goes over there to sniff, at which point I firmly tell him to get away from that spot. I'm thinking of having him neutered because he still has all his "equipment" and I was told by a specialist that this could be the reason why he is so aggressive and beginning to mark things in the home although he knows he is not supposed to do that. Can anyone shed some light on this? I truly do not want to take away his "berries" if I don't have to. However, if it becomes more of a problem with him being so aggressive toward people and marking the home, they will have to go. Although he has never bitten anyone while growling at them and seemingly attacking them, I'm afraid that if it's not taken care of early enough he will get used to it and may, eventually, hurt someone. Although I know a LOT about dogs having raised them and been around them my entire life, I don't know it all and I'm sure I can learn new things. If anyone can help, I'm open to suggestions. -HELP ::From The Lips Of An Ainjell::