Wrong. There are multiple points that come in play here, none of which are as simple as "the activists are protesting against Nazi and conspiracy crap":
First of all, linear TV, radio and newspapers had human reviews in the loop at every stage: client, producer, ad broker, station/paper. That meant that the chance of valuable ads appearing next to bullshit was somewhat next to zero - and also, that "fringe content" was restricted to unscrupulous (or from the same niche) advertisers. Essentially, there was a feedback loop: content that was not mainstream-worthy had no chance of being financed.
Internet advertising and especially social networks with monetization and targeted advertising however, turned up all of that. Suddenly, a Nestle ad could run as a front-roll of Alex Jones lunacy. The result was that an awful lot of really awful content creators had both the technical capability to reach out to millions of people (thanks to the Internet, which eliminated the traditional gatekeepers) and the advertising income that was previously reserved to mainstream-able content.
The result of that, in turn, was an explosion in numbers of these "content creators" and their content (simply because many of them could now actually afford to quit regular jobs)... and thus, combined with the explosion of followers of such content, meant minorities had to suffer from a constant barrage of both online hate speech and real world violence - including many acts of terrorism that claimed human lives, and culminating in the events of January 6th 2021.
What the "extremely small set of activists and journalists" is doing is attempting to rein in the hate and the violence that results of it. And yes, making brands and their advertising agencies aware of what is going on and where their money ends up is a good thing.