Something that can be observed regularly in discussions, is that people are talking and they are not actually sharing common ground.
>>> position A
something unrelated, not position A <<<
>>> position A + concession A.1
This is somewhat relating to the technologies of how to talk and make arguments, but I think more than that, it's a social / political failure on part of the person of the left. A failure to recognize that "discussion" isn't happening and that the other person being talked to, has abandonned the concept of discussion, discourse, compromise and cooperation.
They are sitting at the negotiation table, not to reach a deal, but to deceive and to delay and to distract you from taking measures that will enforce or enable discussion.
You may think it's still a question of compromise and are offering concessions and cooperation on other topics. This will not work and only increase your losses.
Examples of this are topics like