I'm assuming this is a 'Thunderdome' style dog park - basically a fenced grassy or dirt lot? Some areas have dog parks that are massive and include wooded trails, ponds, etc, but they're rarer, so I'm going to give advice based on the assumption that it's the first setup.
Very, very few dogs are good dog park dogs. The environment is chaotic and unpredictable, and gives dogs very little ability to get away from each other or diffuse situations effectively. It amps up excitable dogs to the point where they are incapable of polite doggy play behavior and stresses anxious dogs out. Even if you have a real stable, easygoing, even-tempered dog yourself, you can't control who else shows up and introduces a dog who isn't suited for the environment. There's often very little to do in a dog park aside from interact with the other dogs, so this can make dogs fixate on each other and escalate relatively minor conflicts to something potentially dangerous - they can't decide to remove themselves from a mildly uncomfortable interaction easily so things get heated (think young kids in the back of a car fighting because one keeps looking at the other funny). All of this becomes even more difficult if you have a new dog you just don't know very well yet, because it's harder to spot situations or doggy play styles that will be poor matches for your boy.
A muzzle is a great tool, and I absolutely think it's a good idea to get one and train him how to wear it happily and comfortably (check out the Muzzle Up! Project for great tips and advice on how to do this, if you haven't already). But I wouldn't suggest it for something like a dog park play situation where your dog is already stressed and unhappy. It can make him feel like he has to display sooner and more aggressively because he knows he can't defend himself if he can't make the other dog back off.
These days, I only use a dog park when it's empty to let my boys a quick run, or when I want to do some off-leash training in a bigger space than I otherwise have available. My older dog, who did go to dog parks when he was younger, became less and less tolerant of other dogs because he was stressed by the chaotic environment. He started instigating fights and overreacting to other dogs behaving in ways he didn't like, we believe in an attempt to exert what little control he had over the situation. These days he only interacts with known family dogs, and that's fine. He's much happier, and we're seeing slow, continuous improvement in his reactions towards strange dogs we pass on leashed walks. We're doing some training to help with that, but making that commitment to stop putting him in situations with other dogs where he felt so uncomfortable and out of control that he 'had' to get nasty was a big step forward.
Most dogs don't need socialization with other dogs if they have enough attention and interaction from their humans. But it's much better to arrange playdates with dogs (and owners) you know and trust and who your dog gets along with. Things like parallel walks (two or more people walking their dogs around an interesting place together, like a park or trail) are also often much healthier social bonding experiences than the kind of high-energy, close-quarters play you find at a dog park.
