While everybody was meatposting, i learned about yet another case where the SPD acted as traitors to the working class: the Hamburg Jelly Troubles of 1919, also known as the "9 days of disgust". And it also had to do with meat! So here's what i found out.
This was a case of spontaneous uprisings due to the food insecurities that plagued Germany towards the end of and after WW1. Locals in Hamburg had been looting bakeries and rioted for quite some time, but the biggest uprising started on 23rd of June in 1919.
It all began when a barrel broke in front of the tannery of Jacob Heil, who had branched out into producing cans of jellied meat to profit off the food scarcity. It had been clear for a while that he probably didn't use the best ingredients, but the horrendous stench emanating from the broken barrel made people inquire what was actually going on - they entered the factory premises and came across rotten carcasses of rats, dogs and cats. Later trials couldn't determine whether he used all of that shit to make jellies, but it was proven in court that at the very least he used slimy, moldy cowhides already crawling with maggots. The angry mob decided that they'd be having none of that.
The punishment of the factory owner was documented in the form of cartoons: Heil was pummeled mercylessly and then forced to eat some of the raw, rotten cat meat . The crowd presented some of the cat and dog pelts on the market square and threw Heil in the river, where he almost drowned . The riots soon spread and factory overseers were carted through the city while being publicly forced to eat the digusting jellies produced under their watch.
A siege of city hall ensued. Things got heated quickly when reactionary forces tried to push back by spraying the crowd with fire hoses, which did next to nothing, but was still celebrated by chuds as seen in this cartoon. Things escalated quickly and 14 members of a local Freikorps got killed, so Gustav Noske (SPD), minister of defense, sent in 10.000 troops, led by Paul von Lettow-Vorbeck , who had previously taken part in subduing the Boxer Rebellion in China, had participated in the genocide of the Herero and Nama peoples in Namibia, had fought a guerilla war against the British in Africa during WW1 (mostly sending local conscripts into the fray), and who now clamped down on the rioters in Hamburg without mercy, bringing the death toll up to more than 80. BTW, Lettow-Vorbeck would soon afterwards became a leading figure in the failed Kapp Putsch, a restorative coup attempt that remained a focal point for restaurative forces throughout the Weimar Republic.
I couldn't find any English sources on these riots, but i hope the linked pictures speak for themselves even if you don't understand the text. Here's a syndicalist source on the whole incident, which was the most detailed leftist writeup i could find.
Forgot to mention it in the OP, but the SPD had an absolute majority on the city council and they still preferred not to do things on their own, but to form a coalition with the center-right DDP. It's as if they were doing a "Biden working across the aisle" bit.
Also, having no redeemable qualities is something they have retained to this day. Yes, the SPD is still a thing and they've actually been part of the German government during 20 of the last 24 years, and during 16 of those years, they've helped to form conservative-led governments, sometimes in spite of the option to form a leftist coalition and dethrone Merkel. But hey, they still pretend to be leftists and they even still call each other comrade.
It's baffling to me how there's still people who vote for them. Like, why don't they at least just fucking vote for Merkel and cut out the middleman? Seems like that's changing though.
I think their main demographic are boomers who treat politics like soccer. But i can never totally shake the impression that some of them just want to be dominated by the CDU. Like some kind of FinDom kink, but political.