different strokes..

I dunno whether its just me, or a more widespread difference in the way different communities interact with each other.
Earlier this morning, just after class, I looked over at one of my friends and very nonchalantly said "man... you look like you've just crawled outta the ground".. A bit of an exaggeration, but she was clearly not having a good morning.. It was what I figured was an appropriately inappropriate comment.. She dint say much, but gave a "dont tell me something I already know" look. On leaving class however, a couple of other kids in class told me that that was an incredibly rude thing to say..!
Now I hadn't meant any offence by it, and it was clearly in jest.. But they said that even in jest, it was a highly imappropriate comment.
I was told "perhaps you can talk like that to boys, but not to girls"
Now this to me is a completely novel concept. When another person is my friend, gender ceases to be an issue. Whenever I talk to my female friends, it never occurs to me that I'm talking to a "girl".. Just another one of the dudes!
This hasn't been a problem all through college. Most of my friends being girls, were not spared. From simple insults on how fat they were, to how badly they dressed, to how dreadful they look, they got the hard, honest truth (and mebbe a bit more). And to be perfectly honest, I expected the same from them
But here.. its totally different.. Boys should "watch what they tell girls". Even best friends aren't "brutally" honest with each other. I promised my pals here that I would try my best to keep my foot out of my mouth, but I really dunno how thats gonna pan out.
So why the difference?
was it that my interaction with friends from college was just different from how normak people interact with each other?
is it a difference between friends in india, and friends out here?
or is it just that people in grad school are more grown up, and hence expect me to grow up too (i'd like to see THAT happen).