Q:

What to do about biased question-askers who accept an answer because its supports their bias?

This question and this question brought this to mind.
Questions like these, where the requester is asking a biased question not to gain actual knowledge but simply reinforce or spread their bias (note that I don't mean biased as "wrong", but just biased) are usually put on hold or closed, as with the two above, but when they accept a poor answer that only serves to reinforce their viewpoint, is there a way to remove acceptance of a bad answer without deleting it? 
I understand this may become too subjective, but worth discussing.

A:

This problem is as old as Stack Exchange, I guess. In the end the question author has sole authority to decide which answer to accept. We can not override their decision, except by removing the answer altogether.
What you can do is:

Post a comment on the question where you express your concerns about their choice of accepted answer. Hope they reconsider. Assume good faith. New users might not yet realize that Politics.SE is not an opinion popularity contest. 
If the answer has salvageable content between the bias, consider making an edit to remove the bias.
Downvote the answer to warn others that it might not actually be a good answer. Remember to leave a comment explaining what's wrong with the answer, so others know why it was downvoted and so the author can learn to write better answers.
Flag the answer as "very low quality" and hope the people on the review queue agree to delete it.
If the answer is so biased that it might offend people, flag it as "rude or offensive" and let the moderators decide if it should be deleted.

Also, if the question itself is biased, downvote the question itself and vote to close as "promotes or discredits a specific political cause". Closed and low-score questions disappear from the frontpage and from search results. Nobody will find the bad accepted answer if they don't even find the question.

A:

There's actually a gold badge for this: Populist, where your question gets way more upvotes than the accepted answer.
You're not going to get away from it, sadly. Accepted answers are, by definition, solely within the purview of the OP, and indicate the approval of the OP as answering their question, biases and all. An accepted answer does not necessarily indicate a good answer either.

A:

I have a problem with this specific meta question because it seems to suggest that there are people who are not biased or viewpoints which are not biased. I don't think such people or viewpoints can exist for political questions.
I think what you really mean are people who are asking rhetorical questions because they already know the answer. Those people who are not really asking questions, but trying to spread their worldview. In this case the "promotes or discredits a specific political cause" flag is exactly the thing to ask for, but for all other cases I do not see any benefit for the following reasons.
First, the political landscape is vast and very different in different cultures, so what exactly do you mean with bias? A french anarchist, a German environmentalist, an US libertarian, a Zulu from the Inkatha party, an Israeli soldier, an Indian BJP party member, a Tunisian Muslim? Everyone will give you pretty good reasons for the worldview they have. Even the average Joe is pretty different for countries and cultures, so what should the benchmark be?
For all intents and purposes the best you can do to be impartial is citing only facts and documents. But even they have been selected from a pool of possible documents, they can be interpreted in different ways, (and yes, it is possible that several viewpoints can come to different valid(!) conclusions), you cannot read minds and you don't know the exact, often confidential, reasons for some decisions, so even with best effort you cannot make more than an educated guess.
So what if the "poor" answer is actually right or at least plausible, but violates your own bias? May I remind the threads where left-leaning people are complaining about right-leaning bias here and vice versa? If Politics.SE wants to be "unbiased" as best as possible, your question is, if taken word-for-word, a kind of oxymoron.

