Given the unlikelihood of persuading the differently-minded and already committed in a political debate, why bother?
(1) To persuade fence-sitters and bring them over to one's side. (2) To reinforce the 'already converted' in the tenets of the 'true faith' and provide them with further dialectical ammunition. (3) To oppose and confound those that one takes to have incorrect views while standing up for what one takes to be correct views. (4) To further refine one's position. (5) To enjoy the highest and most reliable of all pleasures, those of the activation of the intellect.
Can you think of any other good reasons?
I am assuming that poliblogging to persuade one's opponents, though a reason, is not a good reason given the unlikelihood of appreciable success. Is my assumption warranted?
Related Posts (on one page):
- Persuasion, Tone, and the Blogosphere
- Five Good Reasons for Poliblogging

You lost me with your last two sentences.
2. Disallowing comments from a particular person, or deleting an offensive, off-topic, or otherwise substandard comment, has nothing to do with censorship. People who think otherwise confuse censorship with lack of sponsorship. I am under an obligation not to interfere with anyone's exercise of legitimate free speech rights. But I am not under any obligation to aid and abet anyone's exercise of free speech rights, legitimate or illegitimate.
3. The Comments area is not an open forum for anyone to say anything about any topic. As the name implies, it is primarily for commenting on the author(s)' posts. But to comment on them, one must have read them. And if I have spent three hours on a post, a reader will not understand it in thirty seconds. Secondarily, the Comments area is to facilitate civil discussion between and among commenters as long as the discussion remains on-topic.
4. Some undesirables: The skimmers, those who cannot read but only read-in. The sophists who, abusing argument, argue for the sake of argument. The ideologues, those who are out for power, not truth. The uncivil. The illogical. The politically correct. Worst of all, perhaps, are those who exemplify the anti-Socratic property: those who think they know what they don't know. If Socrates was famous for his learned ignorance, these types are marked by their ignorant unlearnededness.