2) The reader is wrong. There is so much individual variability in body builders' mental health that this study could not find that the mental health of the body builders was better than the general population.
2/\) is incorrect. Statistical tests are done to examine this potential problem. One of the major reasons we use statistics is to see if any group average difference could be just individual variability instead of a true group difference. If there were too much individual variability there would be no statistically significant difference between the groups. If you picked 2) review statistical significance to sharpen your understanding of this concept