dafbiyun,
We teach children not to use some words, not because the words are themselves vulgar but because children will use them in an improper context. I did not hear the shiur you are discussing, but I have listened to shiurim on hilchos nidda before. Where the crowd is not knowledgeable enough to understand the Talmudic terms (and especially out of town) the Rabbi will use the correct English terms even though a child using the same terms would have had his mouth washed out with soap in our schools