It is interesting how we call one thing terrorism and another protest.
Take the worst of BLM in summer, with hundreds of businesses looted and destroyed in Minneapolis. I remember then thinking "Hey, if you're going to wreck stuff, wreck government property", but broadly condemning the violence. Now we had people (who are factually incorrect, mind you) thinking Trump won, and headed to the Capitol to do something akin to looting.
What is the difference? I don't think there was any expectations that it would actually bring about change. These people (mostly) could not have thought they were actually going to overthrow the Congress or persuade them to reject the Electoral College vote. To me, that puts them perhaps in the "protester" column rather than "insurrectionists" column. A liberal may think I'm being generous, and I am, but it is required for the sake of discussion.
The main differences then, as I can see it:
The protests in summer were widespread, and mostly peaceful,without property damage outside a handful of cities - whereas this is an isolated event. Thus, the comparison is already weak.
The violence in summer was discouraged by most liberal politicians, whereas the president egged this on until the end. Even is is so called call for peace, he continued his lie, praised the protesters, and failed to call in the National Guard.
The protests in summer occurred in a number of places, and tragic as the violence and damage was, it did not have any one focal point or symbolism. The Capitol is the home of our democracy, and the protesters there wished to interrupt that process. Bringing me to my final point:
The fight for racial justice is noble. The history of police brutality is documented. Decades of attempts at reform have stalled. These Capitol protesters have a false grievance. They are a group of conspiracy theorists whose anger is based on lies pushed by Trump and friendly propaganda organizations, and a number of Congressional members. It had no basis in fact, and its call to action wasn't a bill signing, it was the nullification of an election.
Speaking for myself only, I don't support violence. It is a last resort after all other options are exhausted, and I don't think it helped BLM, and I don't think it helped yesterday. I do think, though, that one can empathize with one group more than another. And I empathize with people terrified of their own government for getting beaten and shot and incarcerated more than I sympathize with anti-democratic conspiracy theorists backing a criminal, narcissist, incompetent leader flailing over his sound defeat in an election.