As for me, I'll take the cameraman's word for it. Irwin knew well the behavioral patterns of reptiles. He grew up with them and studied them extensively. It's like the whole Siegfried and Roy thing. Around something you know well, you are not entirely safe, but Roy had worked with tigers for how many years before the incident?
Steve Irwin dives and is filming. He swims over a stingray and the cameraman is blocking the ray's forward means of escape. Ray feels threatened and decides to act. It's way plausible with no intentional "pestering". Even a longtime diver may not be throughly knowledgeable of stingray behavior.
He got in a situation where he wasn't as fully knowledgeable as he was with reptiles, yet he was still confident. Heaven's how many times had he done this type of thing before? The fact remains that a wild animal is still a wild animal. What it may percieve as a threat, who knows as it may vary from animal to animal. He got caught in the kind of incident that everyone knew would happen but are shocked by when it happens.
What flattens me is the whole absurdist irony of this. Is it the Black Mamba that kills him? No. How about the King Cobra? No, no, not him either. Saltwater Croc?!?!? Nope. What kills him is an animal that is traditionally believed to not inflict fatal injuries.
My prayers go to his wife, kids, and parents. What a loss.
Peace
Kevin