I think the idea is to use all the bias-avoiding techniques you can, while trying to find the truth; but to use metaphor and other rhetorical tricks, when trying to persuade others of the the truth.
Overcome our own bias, promote the bias of others?
If one believes the truth for (partly) wrong reasons, is one biased?
If one is led to reject an old bias by convincing rhetoric, is one biased?
I think the idea is to use all the bias-avoiding techniques you can, while trying to find the truth; but to use metaphor and other rhetorical tricks, when trying to persuade others of the the truth.
Overcome our own bias, promote the bias of others?
If one believes the truth for (partly) wrong reasons, is one biased?
If one is led to reject an old bias by convincing rhetoric, is one biased?