Disputed. Some people are naturally on the defensive even when debating true propositions. Defensiveness though is more often a bad sign, since somebody defending a false proposition that they know on some level to be false, is more likely to try to hold territory and block opponent progress. Many advocating true propositions very commonly go on the offensive, nor is it clear to me that this is always wrong in human practice.
I agree, besides which, if there is a popular rule, sign, or proxy for determining who is on the better side of a debate, you can bet that the intellectually dishonest fellow will start waving the "I'm right" flag.
Another month has passed and here is a new rationality quotes thread. The usual rules are: