A) Jill Stein ≠ left politics
B) “proper left politics” involves doing more than just running as a presidential candidate every 4 years funded by the political party in farthest opposition to your political agenda.
That's because we have a Russian plant at the helm of the only, let's be honest, sort-of-not-really viable third party in this country. We need an overhaul of our voting system to get out of this mess, like with RCV
Correct; I think tankies pretend leftism is a coherent thing (particularly one that includes them) because it helps them infiltrate, corrupt, take over, and destroy leftist projects.
The negation of this fiction is an attack against them for that reason.