The author never suggested that everyone who suffers from a fear of heights will engage in activities to try to confront those fears. Some people might not be aware and might not do anything to confront their unknown fears.

This raises the possibility that the causal relationship between risky sports and self-confidence is reversed. People who start off with higher self confidence are more likely to participate in risky sports, which could explain the correlation we observe.

This has no clear impact on the argument. If anything, this might strengthen the argument by suggesting that it’s not a lack of confidence that causes people to choose not to participate in risky sports.

The author never suggested that risky sports are the only way to confront one’s fears. We know people who do risky sports often do so to confront their fears, but maybe people confront fears in other ways, too. This doesn’t suggest risky sports might not increase confidence.

This has no clear impact on the argument. This doesn’t provide an alternate explanation for the correlation between risky sports and higher self-confidence, nor does it provide evidence suggesting risky sports might not be the cause of higher self-confidence.