Both of those guys are idiots. At first, when the guy refused to give his address, it seemed like he was an illegal and was trying to evade detection. It's completely understandable that the cop persisted. Should the cop have backed down? That would be weak as fuck. Guy says he's not doing anything wrong and refuses to cooperate, cops simply accepts that? Not at all. Cop rightfully will be asking himself why this guy is so uncooperative. Was there racial profiling going on? Maybe, idk, would the cop have challenged a white guy? I haven't got a clue, and neither has anyone else. Only the cop knows if he's looked at the guy and thought "he's black, let's question him". I doubt that's what the cop thought, but maybe he did, idk.

The cop is an absolute wanker though when he starts threatening to tase him and pulls the gun out, saying the guy's litter picker is a fucking weapon. What a prick.

Cop should simply follow the guy until backup arrives, and then leave the questioning to his colleagues. That would show a desire to diffuse the situation while still doing his job without backing down.