By Halacha, is Lashon harah about noahides prohibited? I ask partially since I recently saw two older (jewish) individuals who I recall face to face confronted (aggressively) a young gentile who tried wearing a kittel to a Yom Kippur service I attended (he apparently had permission from the rabbi of the shul, so they were offended and I believe gossiped until they forced him to take it off lest he be kicked out), was such behavior against Halacha?

As follow up, I thought for havdalah drink and the drink for Saturday kiddush, a chamar Medina (such as etrog liqueur) is permitted (not for Friday evening shabbat). Secondly, is the principle of using a mitzvah object for another mitzvah an optional mitzvah, a chiyuv, or merely a minhag?