Maybe the title is link bait, but I don't think this is "sexism" by definition. Sexism:
"Prejudice, stereotyping, or discrimination, typically against women, on the basis of sex."
A bunch of males were hitting on the author, crassly or awkwardly, but they were not denying the author equal rights. If a female asked a male to show their privates, no one would call it "sexism"; it might be rude, uncalled for, or strange, but not sexism. At a place like DefCon, most of the males are probably not regular bar-hoppers -- they mostly introverted, and probably fail miserably when trying to approach the opposite sex. (Not to knock on anybody, I am introverted/awkward myself.)
Long story short, if you step into a bar full of males who normally have few opportunities to make contact with women in a social context...yes, you are stepping into the lion's den. Males are sexual, but not necessarily "sexist" -- don't confuse the two.