Hey Child,
I don't know the answer to why some people like to hassle new students. I really couldn't even begin to try and understand that one. But, I have been hassled and in the begining it was hard to deal with it, especially when I didn't know what I was doing and really needed to depend on these people to actually teach me. Abusive + dependence did not make a good combination.
As I have figured out what I need to be doing, if someone gives me grief I just 'ignore' it and keep on going. Most people will stop when there is no reaction. I have also learned to smile alot more which seems to change weird dynamics. A big toothy smile works wonders.
Anyway, I have found that sometimes on a new rotation some people like to give me a hassle but it usually fades. Does this stuff stop in fourth year? I would imagine it never stops to some extent. There will always be someone who wants to get a rise out of someone else, some people are just hardwired that way. People get competitive, anxious, scared and these feelings can get funneled through aggressive behavior towards others who look 'soft.' That's life. I have also found that if I don't react to it, and remain professional, often these people come back around and are very good to me. At least, these have been my experiences.