You do not have to be an activist per se to be on the receiving end of doxing and harassment, unless you count anyone who has ever given public testimony before the legislature, school board, or other body about a subject or who speaks out against troubling activity an activist.
I guess you could in one sense but to me that is somewhat disrespectful of what people who do campaigning and coordination as well as more disruptive forms of activism and advocacy actually do.
And yet, people absolutely will stalk and harass you for giving public commentary at meetings of government bodies. For me that is more personally frightening than the FB trolls because it's people who are definitely in your community.
And people within groups often eviscerate each other. The worst case of harassing grossness that my kid has faced was from a couple of people in a trans support group who decided he was transphobic because he disagreed with them about whether or not everyonr should immediately cut someone out of their life for using their dead name. Not that he disagreed that no one should, just that he personally did not always. That lead to a short time of intense threats (including rape and death threats) and a longer period of online harassment. He and I have both faced harassment and face to face name calling because of our public advocacy in the school district, but nothing that intense (I think because unlike online stuff where you don't have the identity or real location of the person doing the harassment, police will take seriously a member of their community texting death and rape threats to a minor, and people k know it.)
The most death and rape threats I have personally received came from my efforts (combined with others) from within a political party to remove from their position and toss out a long standing and popular political organizer who liked to rape young women at after hours events after getting them alcohol. We succeeded after a very ugly fight--he is out as are a few other people who had been doing other gross stuff that did not involve assault for years, and put an end to the good old boys party culture at state events. But not without a lot of really horrible pushback and personal attacks. Especially since as an elected party official your personal info is usually public information so. It was really intense.
In all cases did I or my kid "deserved" this, I suppose so. We did after all speak up, publicly even if it wasnt rah rah rally activism. I have done that to and while I am mindful of police violence potential as well as crowd danger, to be honest I feel safer doing demonstrations than I have putting my words on record. It is just kind of the price of active citizenship. For every person regardless of political view that speaks in a public and on record fashion theres going to be a ton that will really go after you where they think nobody can see.
This happens to people who write and produce art that touches on any kind of social issue, regardless of side, and due to biases and other long standing things as far as publishing industry and other corporate oversight I'm unconvinced that the majority of people who are left out in the cold are people who dont have "snowflake" sensibilities. Pretty sure there is much more suppression and lack of support for "nontraditional" authors and artists. I just think maybe there isn't as much, so that paltry change feels like a groundswell towards people who feel threatened by it.
That's a human nature thing, though.