The word mansplain is thrown around a lot, but in this case, it applies. You're assuming that women can't appreciate the same kind of jokes that you enjoy and that all of us agree with your assessment that Letsrun as misogynistic and low effort.
Maybe I don't want a "classy" discussion board, or I think the benefits of a somewhat open discussion outweigh the random misogynist joke. Also, I like discussing non-running things with runners, so I don't care to frequent Reddit's advancedrunning community.