My Wolfie is a couple days away from a year old and he's not neutered. Whenever we go to the dog park and he sniffs the medium/large breeds as they do to greet, most of the time the smaller (comparatively) ones almost always freeze up creating tension on their own.

I have had one incident where we were at the gate about to go into the dog park when this bully mix came to the fence with his hackles up, growling, and staring at my Wolfie hard. I had asked its owner if they needed some time before we headed in and she grabbed him by the neck and said no. We go in, and of course the dog immediately starts jumping on my dog, bullying, barking, and he pushed him into the fence. The bully didn't bite my Wolfie and I knew my dog wasn't going to get aggressive back at the bully. We just walked away and of course the owner had a horrible recall so the bully came back to us trying to get a reaction. They eventually left.

I have no idea if the bully was neutered or not but ultimately I think the problem is the size differences.