Well, I'm in my 60s and have been around or owned many dogs during my life. Not too long ago one of my neighbors took in a pit bull. I made it quite clear to the pit bull owner my negative opinion of this breed and that it would have a serious problem if I ever found it in my yard. Seems some of my other neighbors voiced the same thing to this owner and he got rid of it.
Another breed I have a problem trusting are Chows. When I was a kid, there must have been 20 dogs owned by the people living along our block and the only one we worried about was a chow. Mean dog, that on occassion would get out of its fenced back yard and attack any other dog or cat that was out. It also would act aggressively to any kid too, often giving chase to us. But the experience I had years later when living in an apartment, concerning 2 chows, would fix my distrust of this breed. Young couple next door in the apartment complex had two full grown chows, male and female, that they had acquired as pups. The chows were well trained and obediant to commands. I owned a lapsa alpso at the time and these chows got along great with my dog, often playing with each other whenever the dogs were together outside. One day, I had a phone call from the woman with the chows, all she said was "to please come to my apartment right now, I have a serious problem, the door is unlocked" She was speaking in a whisper on the phone, but I could detect the fear in her voice. Not knowing what to expect, I grabbed a baseball bat I had and went next door to find the chows had frightened her so bad, she was standing on their kitchen table. The dogs were sitting on the floor next to the table growling at her. Yikes! The chows were so intent on her, they ignored me and I was able to walk into another room, call the dogs to me and shut them in it. The woman was quite shaken by the dogs turning on her and she could offer no explanation for it. Neither her or her husband had ever had any such problem with their chows before.
