First off, it's a rude thing to tell someone out of the blue that they are "shy." Shyness is usually viewed as a weakness and telling someone they are weak is, well, not nice. It's understandable that any of us would become irritated or even angry if you've heard it enough times (Yes, I blew up on someone a couple times for badgering me about being shy and quiet).
Also, don't forget that people calling you shy are....not shy, lol, so calling you shy is a double standard. I'd imagine you probably didn't tell them that they are "loud," "never shut up," or "talk too much." Them telling us we are shy is the same as saying we "talk too little," which is the same as us telling them that they "talk too much," hence, the double standard.
It's funny because they are doing something to us that they definitely would not like if we did what they are doing to them. Of course, most of them don't understand that because they decided to do it in the first place, but it is true.
