I tend to often use they and their in a generic way like that too. "I don't know what they think they were doing!" "I saw them walking down that way." "That isn't my car, it's theirs." All of these could be in reference to a single person. I think I just don't take the time or care to process such statements to even think of if the subject is a man or a woman. No one ever said a thing about it until the trannies all started taking possession of pronouns.