Being intact does nothing, and please do not chop away vital organs on the dog.I stopped bringing my Bullmastiff to the dog park when he reached about 10 months in age. He was just a jolly guy who liked rolling around and running with other dogs but I sensed that he started to become a target for some breeds. Likely because he was/still is intact. The owners of the aggressive dogs always remained anonymous and just stayed in the background and let things happen. As my breeder once told me when I mentioned dog parks to her that one of these days the personality of my Bullmastiff could change and he could end up doing serious damage to a dog that is looking for trouble. It ends up being the owner's fault of the bigger dog no matter which dog started the trouble.
Some dogs just end up being a target, my friend had a 75% Neapolitan Mastiff cross (Bandog) that just became a real target for other dogs. I'm not sure if the Bullmastiff would tolerate that as well as his Neapolitan x did, because the Neapolitan never got its skin broken and it would hold down dogs like Golden Retrievers but go full in on dogs like Staffies. Always proportional depending on the dog.
I do believe it's a wise decision to not allow real dogs at the dog park, whether it be a working GSD, Jagdterrier, Bullmastiff etc. etc., as everyone there will scream and cry when their wuss dog instigates a legitimate dog... I wish it wasn't that way though.