The original "tankie" incident, the one that gave the term its name, came when the Soviets invaded Hungary in 1956 to crush a workers' uprising. "Tankies" were those leftists who followed Moscow's line in supporting the invasion, dutifully repeating Soviet propaganda about how this was "anti-fascist" or how it was responding to "American aggression", despite the fact that under any objective metric it seemed a straightforward form of imperialist aggression by a powerful state against the very democratic and labor forces that these same leftists claimed to stand in stalwart defense of.
Most of us, of course, were not around in 1956 and so missed the opportunity to be original tankies. But all that's old is new again, and we now literally are faced with a seemingly imminent decision by Russia to once again send in tanks to invade southeastern Europe! And the Democratic Socialists of America have responded by showing just how excited they are at the chance to fly their tankie flag high. Their statement that regurgitates every predictable horseshoe-theory trope about why Russia is really the victim here, everything bad is America's fault, and "solidarity" means telling Ukraine it deserves what it has coming to it. Way to seize the moment, DSA! Who even cares that Russia is now itself a right-wing kleptocracy? It's adverse to American interests, and that's (apparently literally) all that matters.
It's a side issue, but I think there were some Jewish progressives who had some sympathies with the DSA, at least on matters of domestic policy, and were accordingly a bit rattled by the DSA's decision to go all-in on backing BDS in its most extreme and uncompromising possible form -- not because of the "trend" it did or didn't portend, but because it caused them (the Jewish progressives) to second guess their own instincts that were averse to BDS. If the DSA is a reliable guidestone to good progressive policymaking generally, what does it say that I'm bucking them here? It is, I imagine, a relief to remember that the DSA's foreign policy approach is consistently terrible, anti-democratic, and pro-authoritarian (see also: Venezuela), and that there is absolutely no reason to feel even remotely anxious or skittish if you end up on the opposite side of the argument from them.