Are not protests and demonstrations a part of activism? Or am I being tainted by my memories of Vietnam (my older brother was of draft age, so I was aware of a lot of peace protests, burning draft cards, burning bras -different issue-, and I even remember bracelets engraved with the names of servicemen who died in 'Nam)?

Part of activism, yes. But not all of it. Perhaps not even the most important part.

You can't actually change policies with protests and demonstrations. That was the major failure of Occupy Wall Street, perhaps the first major "social media" protest/demonstration (long enough ago that it was arguably spawned by Tumblr and not Twitter). They got a lot of attention - but because there was no organization behind it, there was no practical way to translate that attention into actual policy changes. There were no leaders, no hierarchical structure, no mechanisms to internally prioritize goals, no mechanism for sustained lobbying and coordination and all of the boring stuff that goes into an actual movement.

The Civil Rights movement had structure. The NAACP and the SCLC and CORE were real organizations, with staff and membership and a group of people who held positions of real authority. The problem with "leaderless" movements that the modern generation wants to have is that leaders are important. They're not just important for motivating people - they also provide structure for decisions to be made, bargains to be struck and honored, and for priorities to be set.

Just telling millions of people on Twitter to show up on the Mall won't do much, even if a million people show up for your event.