Is it normal not offended by period talk?
I was out grabbing a few beers the other day and was pretty much the only guy in the building at the time. This group of women started talking about their periods and whatnot. They forgot that I was nearby, and then they started apologizing to me for talking about their periods. At no point did their talk offend me.
If you're a straight guy, I don't know why hearing women talk about their bits should bother you. Honestly, I get a little turned on sometimes when women start talking about their bits; most male primates with the exception of the human male seem to get horny in the presence of an ovulating female, so I don't know why things are so weird for us.