If the other employee isn't your manager or managee, are you really suggesting that "Do you want to go the the pictures tonight?" is in any way related to sexual inequality?
True story: A couple of weeks after I proposed, my fiance told me that the best thing about being engaged was that she could politely ward off workplace flirtation just by holding up her hand and saying something to the effect of, "Sorry, wearing a ring." Before that it was apparently quite painful.
Vulnerability? The vulnerability has been caused by something else, which is the inappropriate behaviour.
Minority? Irrelevant - (at least) one sex will always be in the minority if there are an odd number of employees.
Feeling bad? Unrelated to sex.
Regardless, the behaviour mentioned is neither severe nor pervasive (if standalone) and not intrinsically sexual.
EDIT: From some above comments, you sound like you might be suggesting there is an Atlantic culture device. I'm UK-based, so perhaps this partially explains to you a difference in opinion.
Who are you arguing with? Me, or HR and the company counsel?
The UK has extremely similar workplace gender equality issues to the US according to the World Economic Forum Gender Gap Index; we're basically neck and neck.
I was addressing your experiences with HR and legal departments.
The Gender Gap Index does not measure harassment -
"The Index benchmarks national gender gaps on economic, political, education- and health-based criteria" (from the 2011 report) - so I do not see the relevance to a discussion on sexual harassment.