You aren't in high school.

You aren't facing a clique of girls who happen to all live in the same neighborhood and have radically different interests likes and dislikes from you.

You're facing a group of top industry professionals self-selected from around the region/country/world (depending on how large/prestigious of a conference it is).

And the fact that you don't understand this distinction, the fact that you think it's legitimate for a man to categories "groups of women" as "cliques of mean girls" from high school onwards without reflecting or reevaluating the changing circumstances is why society (and more specifically YOU) still have a long way to go to understand what sexism is and is not.