My view too. Janit0r is absolutely a vigilante, but currently BrickerBot (and the less destructive Hajime) are only active "solutions" to the various IoT botnets such as Mirai and, from their posts, I believe (s)he would stand down as soon as more active steps were taken by the vendors, ISPs, and owners. Far from ideal but, until those in a position to do something about it in a less disruptive manner step up to the plate, if that's the only option for the rest of us caught in the firing line, then I'll live with it. Keep calm, and carry on bricking!
As for this specific incident, although Zyxel has to take some blame for shipping broken routers in the first place, I'd say the main culprit here is actually SierraTel, both for their failure to implement secure central management of their modems in the first place, but mostly for failing to learn from Deutsche Telekom's experience and remediating that error, despite having *six months* to do so. Clearly that has now cost them financially and in customer satisfacation, which should hopefully server as a wake up call to anyone else in a similar situation and dragging their feet over deploying a solution. Somehow, I don't think SierraTel is going to be the only ISP to have this kind of problem though.