Google tailors the ads to the viewer. So maybe somebody else who uses your PC sometimes searches for gay porn on Google.
But... I'm the only one who uses my computer? Could I be such a covert homosexual even I don't know it?
Very funny, but no. Google ads are mostly based on the web-content, keywords and stuff.
I'm the only one that uses my computer, and since I'm not into gay porn, I must assume that words like muscle, muscular, bodybuilding and such...are flagged by them as being gay content. Unfortunately, we female muscle lovers are a minority.
OH. That makes sense. 'kay.