I have just solved this entire threads arguments with perfectly reasonable, calm, logic.
Historically speaking, a Lord was male and a Lady was female. The term Landlord, since it includes Lord is assumed to be male by most. It's not sexist, in the derogatory sense, it's an automatic response.
Speaking in modern terms, Landlord has simply become a term used to identify someone 'Lording' over whatever plot of land you are inhabiting, and is not gender specific.
Evidently, roughly half of the Escapists on here are going by the historic term and equating Lord to male and Lady to female (Which is perfectly reasonable, and not derogatory in any form, by the way), while the other half prefer to use the more modern term, equating 'Landlord' with either gender.
In short, you were technically being sexist, in that you separated the modern, gender-neutral landlord into it's component gender-based progenitors Lord and Lady, but you weren't being deliberately insulting in any way.
You were, however, being rather rude by specifically correcting her terminology with your own because, as evidenced here, different people equate different terms to different meanings.
There, you see? Perfectly reasonable, calm, logic. Insult free and informative.
Why don't more people post this way? As opposed to instantaneously throwing around insults and assuming that, because their opinion differs, they are automatically right, and therefore better?