This is not exercise in defining objective rules about what "is" and "is not" sexist. Sexism is highly subjective, like most social topics. What matters is that a geek girl--supposedly the target audience for Geeklist--complained about a Geeklist video.
Complaints about brand are not uncommon. If you manage a well-known brand they WILL happen, and there are good and bad ways to handle them. Getting the hackles up, subtly threatening the employment relationship, whining about being polite, are all bad ways to handle it.