I don’t think you need to put moral or political judgments on this. As I understand (and I have not really done my homework here), there are two reasonably objective distinctions here:

1. The BLM protests were planned, in public at least, as peaceful protests. Things went wrong and they didn’t all end up peaceful and law-abiding, but I did not see any reports of people using major internet platforms to plan to start riots or cause property damage. The reports of planning of the DC riots on Parler, in contrast, seem to have been quite explicit about the intent.

2. (In my mind rather less clear cut.) The BLM protests were not based on objective lies. The DC riots were. Ignore all the people saying there was no proof of widespread voter fraud — that’s like people saying that there is no strong evidence that MSG causes headaches. In fact, there isn’t even a reason to suspect widespread voter fraud. The proponents of the fraud theory have, when they’ve presented evidence at all, presented comically weak evidence. The theory is obvious BS.