I'm pretty good at picking things up from context, so I'm gonna say a tankie is someone opposed to the deployment of tanks against a captive civilian population, the police having tanks, and tanks' worth of tear gas being used on peaceful protestors?
(please don't reply with earnest answers to my question, thx)
EDIT - some of y'all are failing to follow this last instruction smdh
It's short for 'TrueYankee' and refers to members of /r/yankee who left in disgust for it's insufficient patriotic bloodlust and broke off to form their own sub