Well, it’s for a jury to decide, whether the security guard was justified in using force, and whether the force used was appropriate to the situation.
However, any time you initiate violence and put hands on someone, you give them a reason to fear for their safety, and that creates grounds for a self defense claim.
I’ll meet you part way on that, when the use of force you are defending against is unlawful or dangerously excessive. But you cannot honestly read that in this situation. He got ejected. He retaliated. That is not self defense and no jury should buy into any claim of immediate threat that justified the attack he launched.
Getting dissed or getting a bruised ego is no legal justification for throwing punches.