If there is one thing that dog parks taught me it is that there are dozens of "closet experts" that are willing to tell you your dog's problems and solve them instantly whether you ask or not. Nuetering does help with some behavior issues, I am not denying that, but rough play?? Try a nice long walk or high speed fetch game before the dog park, to aleviate some of the excess energy, and you may find he is less wild. By all means, nueter him , but do it for the right reasons. It is not a magical cure for any and all ills, as the "closet experts" have represented it to you.
Stella