Medical students are one of the most brash and opinionated group of people you will ever meet, probably second only to full-fledged doctors. They love sharing their opinions on anything and everything, even if you don't want to hear them. Especially if you don't want to hear them. And especially if you don't care. If you ever watch a television show with a med student, prepare to have every plot, information, and wardrobe inconsistency identified and dissected at the level of a graduate-degree thesis (complete with bullshit theorizing). The importance of this obstinacy as a survival mechanism cannot be overstated, as it has served them well in their previous 20-plus years of life; pre-med classes are not easy, and this obstinacy is often the only thing driving these students to do well in their classes.
A common misconception is that the majority of medical students are obstinate, which is simply not the case. The reality is that the majority of successful medical students are obstinate (while the rest are cheaters). This is because the more obstinate medical students don't have silly things like guilt and morality nagging at them when they make a mistake or hurt a classmate's feelings, and without these psychological hindrances, they are free to to keep moving forward even when they royally screw things up.
There are a few things med students are especially obstinate about, including liberalism. If you are thinking of going into medical school and you hold any conservative viewpoints at all (e.g., that abortion is wrong), you should prepare to have these views mocked without mercy, especially if you go to a top ranked medical school.
Usually this obstinacy will not cause you too much of a problem, as you will quickly learn to avoid these people in your social circles. However, your classmates' obstinacy can become an issue in small group settings, as you will be forced to sit in the same room with other med students for two hours at a time, with everyone being "encouraged" to share their views on random different inane topics. In order to survive in this setting, always remember that there truly is no one "right" viewpoint, no matter what that annoying bitch says or how loudly she says it. The quieter you are and the more you let things slide, the easier it will be to pack up your things and walk out the door when the small group session is over.