The author doesn’t reject a tactic, she advocates for one.

Like (A), the author advocates for a tactic, she doesn’t reject a tactic. She does note that this tactic “rarely help[s]” the group to reach a consensus, but she doesn’t claim that it makes it “virtually impossible.”

She does conditionally advocate a tactic, but she doesn’t do so on the grounds that it is a less offensive accusation than the alternatives. She just argues that it’s a more effective accusation.

She does conditionally advocate a tactic that results in an argument, but she doesn’t claim that it would help the group reach a consensus on the issue in question. Instead, she suggests it would lead to a consensus that the accused person is indeed "unyielding."

The author conditionally advocates for using the word "unyielding" to accuse a group member on the grounds that it results in an argument where one can't accept the premise (that they haven't yielded on the issue) but deny the conclusion (that they are "unyielding").