I think we can all agree that the 'aggressive' appearing dog is not always the aggressor. It's really hard to tell with out seeing it first hand. If multiple dogs have an issue with your dog though…..it's probably your dog. Regardless if your precious pooch was a rescue, or whatever, dogs don't think like that.
If a pedophile was in a playground adult humans would gang up on that individual....I feel like dogs are the same in that respect. If they sense something wrong they try to fix the situation by taking down that bad presence. That is my dog through and through...sweetest thing you will ever meet UNTIL a dog that has issues comes along. If that happens it's all about protecting the humans....
The fact that Milosh is described as an "alpha" is very telling. It's also very telling that the woman who owns the springer is perceived as rude by multiple people. The springer may just be picking up on negative energy from her, and is a perfectly sane dog. Hard to know..... but we can only offer advice based on the information given. For all we know the two were just playing normally and there is no problem.
Regardless, NO ONE should bring a dog into a dog park with a muzzle on. If a dog truly 'bites' (nipping isn't really biting) then it should not be at the dog park. Period. Socialization classes are for that, not our free time. If you think your dog might be the problem; starting fights, bullying.....then please go to classes not the dog park.
Someone brought a muzzled dog to the park the other day, and it did not stop the dog from showing aggressive behavior...just stopped it from biting..... and then of course all the dogs in the park (who were playing normally up until that point) jumped it. The energy changed 100% due to that one dog; as soon as it was gone things were fine.