Never did soft play. Outdoor parks are cheaper and it's SO much easier for you to monitor what's happening, choose a time of day when it isn't jam-packed.
If it has to be indoors then children's centres and local leisure centres often have quieter times and better trained staff to help you, help your kid. (My local soft plays tend to be mostly staffed by youngsters who have no special SN supervisory training).
Likewise our visits to the big London Museums happen on INSET days and during the winter, never at Peak holiday times.
Prioritise your battles. Once your kid gets past a certain age soft play is a sensory environment they'll never have to cope with again. The school dinner hall threatens to haunt them till they are 18. Outdoor parks are an environment worth teaching him to cope with.
"Walk away" was a mantra I instilled from age 2 onwards thank goodness as DS will now not ever start a fight, despite some pretty awful provocation at times from the local oiks, but physically nowadays he's more than capable of finishing on off iykwim!
Also learn not to feel guilty if your child reacts adversely to bullies. It stops you being able to objectively teach your kid the skills to cope. Notably to stay calm, not panic and get away fast when young, followed by signalling for adult help as soon as they are developmentally able to. He needs to know he has your support 100% in trying to cope before he can begin to acquire any useful skills.