Also, what a joke that the officer basically shrugged and said he couldn't help if no crime had occurred.

So I definitely get where you get that impression but what the article says is (emphasis mine)

After the agent identified himself, the officer told him “he could not assist with someone following or recording him if no crime had occurred, and that local law enforcement was en route.”

Which to me kind of sounds like cop-ese for "She's allowed to follow and record you if she wants, so how 'bout you fuck off before we cause an even bigger scene?"

Now would it have been nice if the cop had arrested the nazi for brandishing or something? Sure, but you're living in a fantasy land if you think that would have gone anywhere. I'm pretty sure any half-decent lawyer in the country could have gotten those charges thrown out because a "law enforcement" officer drawing their gun when they feel threatened while on an "operation" isn't exactly illegal. And the arresting cop probably would have just found himself in hot water for interfering with the "operation"

And it was a Fullerton officer but the incident occurred in Santa Ana, so there may have been jurisdiction issues where he legally couldn't have done much beyond what he did since he was out of his jurisdiction. Honestly a lot of cops probably would have said "not by town, not my problem" and kept driving.