They did not think it was a big deal. It was self deprecating humor, aimed at themselves. It certainly wasn't intended to imply anything about anyone else. If I had tried to convince people that it was something that was going to make foreigners hesitant to post, I would have been dismissed. I didn't bother to try to convince anyone I was right. I felt that the forum owner's clearly stated desire to have more international members was sufficient "permission" for me to feel a clear conscience about rooting out this "humorous" meme. If you think that meme is clearly a big deal but misgendering women is not, I will suggest you are underestimating the problem regarding use of pronouns.
