What if a person said it as opinion: Looting has the potential to initiate shootings. Are we looking at an opinion, an observation, or glorying violence.

If I said that, it's an observation. If the chief of police said that, it's an implied threat. This is because I don't have the power to initiate shootings, while the chief of police does. There is a power differential, and statements can be viewed in the context of the person making them.

This is why phrases like "we should nuke them from orbit", which might be calls to violence if made by a head of state, are generally seen as satire, because there's no chance of me actually nuking someone from orbit. Context matters.

If some hypothetical person said it as an opinion or an observation, you'd have to look at Twitter's policy and try to understand the spirit of the law. Threats are a direct form of pro-violence speech, and glorifying violence is an indirect form of pro-violence speech, so it seem to cover a spectrum to me.

But whichever way they interpret it, all that really matters when it comes to fairness is that they are consistent.

If we look at a very non-hypothetical person named Donald Trump, he wrote "when the looting starts, the shooting starts" immediately after "I won't let that happen" and "the Military" and "we will assume control". Without context, the words could be just an opinion or observation, but in the context he used them, that's not a reasonable interpretation. You don't mention sending in the military (who have guns, obviously) and then mention shooting as a total non sequitur in the next sentence.

If somehow improbably he meant it to be an opinion or observation, he phrased it terribly, and Twitter is within their rights to interpret it how he wrote it.