Working "Girl"

One question I have been asked recently is about gender discrimination. I personally feel that gender discrimination, although it still exists, is not nearly as prevalent as everyone seems to want to believe. The people that find it the most often are the people who go around looking for it.

 And I'm sure you've met those people, every thing is to blame on their gender, or their race, or their religion; but never, ever, could they possibly be just plain underqualified for the job.

Throughout my adult life, I have been a working, professional woman (obviously). I can honestly say that I have never come across any sort of gender bias or discrimination - none that I've seen, anyway. I've always been paid equal or more as men in my same position, have never been sexually harrassed, have never been demeaned for being a female, nothing. But I have come across many ladies who seem to find it where ever they go. How is that possible? Of course, I know it exists; but how can I, who's lived in many different states and has worked in professions dominated by men, not ever see it when there are so many others who seem to find it every day no matter what job they are looking for? Have I just been blind? That's possible. Or maybe I just got extremely lucky that I've never been faced with it. But that's a pretty large discrepency.

Then there are people who see it when it isn't even there, such as those I described above. So, here's my question. What do you think of a professional, working woman being called "girl" in the workplace by a colleague?

 Is that demeaning or belittling in any way? I don't think so; but then there are guys (usually older) who might actually mean it in a somewhat belittling manner. But do they mean it as a demeaning manner regarding gender or age? Is it really offensive to be referred to as a girl if you're working? Would you consider it an insult? If you've ever said it, did you mean it as an insult?