Well, when people believe in such an absurdity, it's going to be pointed out when they are trying to ridicule others, for their "ridiculous beliefs". There is no cut off period, where it stops being relevant to one's logical consistency.
Be honest though, you're annoyed because it's a very inconvenient issue to leftists who claim to be all about facts and science n' shit, and you rather it not be brought up, because it the left look fucking retarded. Yes, when they get all high and mighty over their alleged adherence to scientific fact, it will always be noted that they don't believe in basic biology.