Sudden Agression Towards Men

Question
Hello Diane:
My girlfriend and I own a weimeraner. He is roughly 1 to 1.5 years old and is a rescue. He has never shown any signs of aggression toward anyone or any animal before. In fact, he is a down-right wimp when it comes to face-offs with other dogs. But recently, he has been growling and biting at men only--typically only when they reach to pet him on the head. He has never exhibited behavior like this towards anyone before. The only event that could have had any effect was when my brother yelled at the dog for pooping in the house. I was not home when this happened. Any ideas of why our sweet little boy is suddenly so snappy towards men (not including me).

Answer
Weims are very very active dogs. They are intelligent, high drive and need lots to occupy their time and their minds. How much exercise does he get? Many people feed these high energy dogs high protein dog food and then just do nothing with them. He needs to be walked twice daily briskly until he's tired. He also needs to run at least twice per week until his tongue hangs out, playing fetch or whatever. If you haven't enrolled him in obedience classes, do so, you'll love it and so will he. Get him some toys that occupy his mind and his body. Like Kongs with treats inside. Also go to  alpha boot camp by typing that into your browser where you will find tons of suggestions about getting your pack into order. It is much more than I could ever answer in one post. Weims tend to have personality issues when they are not worked, very often aggression begins with one act and when it is allowed to continue it will grow into other areas of the dogs life. To a dog, coming down on top of their head is an act of aggression anyway. Until you get this worked out, have people scratch him under the chin, or on his chest, not coming down on top of him in any way. If you implement the exercise and restructure your alpha behavior it'll more than likely solve your problem :)
Diane