Well, you had to take it there. O.K. When I was in medical school, in a course called 'Physical Exam' they brought in people to 'practice' the rectal exam. We were told that if one suspects homosexuality (as a medical concern) you can ask the patient to relax his rectum. If he cannot relax his sphinctor, he is more likely than not, NOT a homosexual. If, however he complies with your demand, this is a learned behavior. This is an accommodation response from....well other penetrations.
If your doctor is examining you and he asks you to relax your rectum, he is suspecting something you might not want him to suspect. Lay off of the 'guyliner'.