Keep your hands to yourself. Clearly Embiid wasn't in on it, and he doesn't know this dude. The fan played himself thinking Embiid was going to be cool enough to just let a stranger playfully push him to get a pass just to goof around.
Not everybody can be approached like that. When all else fails keep your hands to yourself. Period.
Edit: On 2nd review it looks like Embiid was the one expecting the pass, but the fan pushed him out the way. Still, a safe rule of thumb is to not shove another grown man for reason, buuuuuuut maybe Embiid shoulda been a little more light hearted. Still perfectly reasonable reaction from him imo.