Here is a case of a Rabbi being asked if going out to lunch with his non-Jewish co-workers would be a violation of marit ayin... And some other issues concerning this concept 'marit ayin'...
http://www.yeshiva.org.il/midrash/outershiur.asp?id=6425Most of us are familiar with the prohibition of maris ayin, avoiding doing something that may raise suspicion that one violated halacha, or that someone may misinterpret, thus causing him to violate halacha. However, most of us are uncertain when this rule applies and when it does not.
Here are some examples mentioned by the Mishnah and Gemara:
A. One may not hang wet clothes on Shabbos because neighbors might think that he washed them on Shabbos (Mishnah and Gemara Shabbos 146b). This is true even when all the neighbors realize that he is a meticulously observant individual.
B. Officials who entered the Beis HaMikdash treasury did so barefoot and wearing garments that contained no hemmed parts or wide sleeves, and certainly no pockets or cuffs, so that it would be impossible for them to hide any coins (Shekalim 3:2). The Mishnah states that this practice is derived from the pasuk vihiyisem nekiyim meiHashem umiyisroel (Bamidbar 32:22), --- Do things in a way that is as obviously clean in the eyes of people as it is viewed by Hashem. Rav Moshe Feinstein (Shu’t Igros Moshe, Orach Chayim 4:82) contends that this type of maris ayin is prohibited min haTorah!
C. Tzedakah collectors should get other people to convert their currency for them and not convert it themselves, because people might think that they gave themselves a more favorable exchange rate (Gemara Bava Basra 8b; Shulchan Aruch Yoreh Deah 257:2).
A CURIOUS CONTRADICTION
The concept mitzvah of maris ayin is a fascinating curiosity because it contradicts an important Torah mitzvah - to judge people favorably. This mitzvah requires us to judge a Torah Jew favorably when we see him act in a questionable way. (For further information on the mitzvah of judging people favorably, see Shaarei Teshuvah of Rabbeinu Yonah, 3:218.) If everyone always judged others favorably, there would never be a reason for maris ayin.
Yet we see that the Torah is concerned that someone might judge you unfavorably and suspect you for violating a mitzvah.
Indeed, a person’s actions must be above suspicion, while people watching him act in a suspicious way are required to judge him favorably.
THE TREIF RESTAURANT
May I enter a non-kosher restaurant to use the bathroom, to eat a permitted item, or to attend a professional meeting?
A prominent Rav once gleaned insight on this shaylah from early poskim who discussed the kashrus issues of Jewish travelers. In the sixteenth century, there was a dispute between the Rama and the Maharashal (Yam Shel Shelomoh, Chullin 8: 44) whether a Jewish traveler may eat herring and pickles prepared and served in non-kosher inns (quoted in Taz, Yoreh Deah 91:2). The Rama ruled that, under the circumstances, a traveler could eat these items on the inn’s non-kosher plates, whereas the Maharashal prohibited using the inn’s plates. However, neither sage prohibited eating nor entering the inn because of maris ayin; from which this Rav inferred that entering a non-kosher eating establishment does not violate maris ayin.
However, Rav Moshe Feinstein rules that entering a non-kosher eatery is a violation of maris ayin (Shu’t Igros Moshe, Orach Chayim 2:40). Why does he not compare this law to the inn of the earlier poskim?
The answer is that in the sixteenth century, the inn functioned as a place of shelter and lodging, in addition to providing food. Therefore, someone seeing you enter the inn would assume that you were looking for a place to sleep, and that you have no intention to eat non-kosher food there. Thus, the sixteenth-century inn is more comparable to a twentieth-first century hotel that contains non-kosher restaurants. There is certainly no maris ayin prohibition to visit a hotel since a passerby would assume that you are entering the hotel for reasons other than eating non-kosher. However, the primary reason people enter a non-kosher restaurant is to eat treif food. Therefore, Rav Moshe ruled that it is prohibited to enter a treif restaurant because of maris ayin.
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I am sorry if this is a digression from the topic. And it is true that if it is available at a kosher market and everyone there knows it is not meat, then there should be no issue. But what if this stuff is on the shelf, with a hecsher, would other Jews and non-Jews judge us incorrectly?