I got the impression that the people doing it was pro-GamerGate but didn't like how the two identities in question (who were trying to speak in support of them) were handling things
Uh, why ? The article doesn't say anything like that. The people threatened are not anti-gamergate, they're pro-gamergate. Without indication that they're being expressly terrible at defending gamergate, logic dictates that they're harassed for being pro gamergate, and until an investigation actually tells us who sent it, the obvious guess is that the threats and harassment come from anti-gamergate people.
The whole article is centered on that sentence "When you bring light to the harassment of Sarkeesian and Wu, don’t leave out the doxxing of GG Feminist, academic feminist, or death threats sent to Boogie, a prominent YouTube celebrity, in the shadows." which is there to say that yes, people from the other side of the argument are ALSO being threatened, not just the over-mediatized douches. And not necessarily by the same people who somehow think that these guys aren't representing them well enough - such an assumption would be a pretty big bias.
A feminist, a gamer, and a journalist writing for TechRaptor and Gamesided, and yet a woman who does not agree with Sarkeesian’s critique, I am an outsider. I have been harassed on Twitter and Reddit, I have had my personal e-mails hacked, and it is certainly not by those who support this revolt. It is by trolls and those who believe that as a woman, I am a traitor to my gender for not wishing to quell this debate, for not automatically siding with Anita. I am a woman who wishes to listen to both sides of the debate, and so I must have internalized my misogyny, I must be misguided, and blinded by the ideas of men. I am now excluded from a community that used to include me.