[Avodah] Maarit Ayin - Sources?

[Liron Kopinsky]

On Wed, Nov 9, 2011 at 1:33 PM, <kennethgmiller at juno.com> wrote:
> My understanding is that Maarit Ayin relates to confusion over whether
> something is assur or mutar...

> But in any case, that's NOT the question being asked. The question being
> asked is about an action which is halachically allowed but socially
> unacceptable. I would think such activities to be not Maarit Ayin, but
> Chilul Hashem...

> I'm not sure what the questioner means by "or just something most people
> are ignorant about". Perhaps he means "an action which is socially
> unacceptable, but people are ignorant about why it ought to be socially
> okay". I so, I would imagine this to still be a Chilul Hashem, because the
> net result will still be that - rightly or wrongly - it causes the onlooker
> to have lessened respect for HaShem and for Torah people.

The questioner was definitely asking about "ignorance" in halacha. Let's
say there is something that can be purchased which is kosher from a
non-kosher restaurant. How do the parameters of Maarit Ayin allow/prohibit
this? For example, we do see frum people ordering a coke from non-kosher
restaurants.