What some vids don't show is that Bart kept following and harassing him multiple times before the punch. Buzz would walk somewhere else to avoid him, and Bart would soon follow, sticking the Bible in his face and taunting him. If you didn't see the whole thing, it may look like Buzz was unreasonable. It shows that video evidence can strip out context if not complete.
There is actually more to the story than even that. Very soon after it happened, the little fuck sent out his video, in which he challenges Aldrin to swear to the truth of the moon landing, and BOOM, Aldrin punches him. But there were bystanders who also recorded the incident, and all their videos had the little fuck yelling "YOU'R A LIAR AND A COWARD AND", and BOOM, Aldrin punches him. In other words, the little fuck actually edited the video and changed what he was saying in a pathetic attempt to make Aldrin look bad.