Although I'm somewhat biased being a Lubavitcher, I'd say that Chabad Rabbis like the one at the bas mitzvah "get paid" for not talking down to not so frum people.I happened to have thought that the rabbi involved showed a much greater awareness of his audience then other rabbis in the same situation would have.
A recent Bar Mitzvah I was at illustrates the point. The Bar Mitzvah boy’s family includes a lot of non-Orthodox relatives from out-of-town. Some are not religious, and some are Conservative. One cousin, himself recently “Bar-Mitzvahed”, is considering attending the local pluralistic Jewish high school in his hometown. His concern, as his mom explained to me, was whether or not he was good enough at the Jewish stuff to attend. I sat next to this boy in shul and his Hebrew reading skills are fine.
When the rabbi got up to speak, he spoke in “Frumspeak, rather than English. The boy turned to me after the rabbi’s speech and said: “I didn’t understand a word he said. It was all conjunctions and “Chhh!” His mom was upset because she thinks that this negative experience could impact on whether or not he decides to go to the Jewish school next year. His confidence definitely took a hit.
I’m not blaming the rabbi for this; he had no way of knowing that aspect of the situation. However, the shiny colorful kippot and colorful prayer shawls at the otherwise Orthodox davening should have tipped him off that a large percentage of the guests would not understand him if he spoke “yeshivish.” As a result, he missed an opportunity to share some Torah and chizuk with people who were open to it. I don’t believe that rabbis necessarily need to dumb down their Divrei Torah for the sake of some less or non-observant relatives, but I do think that a little sensitivity in terms of their presentation can go a long way.