You are right. MD's can definitely be arrogant and belittling. Perhaps it has to do with the fact that, at this day and age, it is generally more competitive to get into med school than it is to get into grad school. Folks who get into medical schools tend to have very high GPAs and go through hell and back to just get into a med school. Does this mean that PhD candidates are dumber? Of course not. It just means that PhD students might have had a little more fun in college. But anyways, some folks who get into med school take it a bit too far once they have overcome the difficult challenge of being accepted...they feel that they are God's gift to earth and are very quick to judge and belittle those who are not in med school. I have witnessed this mentality with respect to med students' attitudes towards grad students, nursing students, pharmacy students, and dental students. These folks will therefore jump the gun to think that they are the brightest of the bright. And when it comes to their perceptions of PhD training, they may jump to the conclusion to think that if a PhD can do X, Y, Z then the MD would sure be able to easily tackle these things.
I think this arrogance of some med students is very unfortunate. The MD and PhD training programs (let's assume that there are no MD/PhD programs) provide people with vastly different skillsets. MD curricula tend to teach critical thinking skills and creative intuition LESS than PhD curricula. On the other hand, MD training stresses that a person master a painstakingly wide array of topics, a lot of them via rote memorization whereas PhD programs will encourage deep understanding of a specific area of science. This makes sense. MD trained folks are not trained to do science! They are trained to take care of patients in a hospital ward or a clinic where they can and will be encountered with a wide array of diseases at a given time. MDs must therefore have mastered a ton of information so that at a drop of a hat, this information can be applied to ill patients correctly and efficiently. PhDs are trained to apply the scientific method to address very specific and focused research problems. PhDs are trained to ask pointed questions and create new knowledge via controlled experimentation.
Hence, MD's are really in no position to comment on what a PhD has to offer in the grand scheme of things. This is because MD's clearly have not undertaken rigorous PhD research training and cannot fully appreciate it. Now if a certain individual with an MD degree decides that he/she would like to dedicate him/herself to biomedical research...then this person needs to get in-depth research training whether it be by doing a PhD and/or postdoc after residency.
I'm not directing this post at any certain individual. I just wanted to post my thoughts because I have grappled with these kind of thoughts. I will admit that when I was starting out in MD/PhD training, I was egotistical and condescending at times...it was like, "ooh look at me, I'm in medical school...i'm the frickin' bomb!" Now having completed the requirements for both the MD and PhD degrees, I have seen first hand what both training paths have to offer. The MD training and PhD training offer very different things and it is pointless to say which is better or more worthwhile. It really does no service to get into these kind of juvenile pissing contests.