GAW: la’aniyas da’ati, I fail to understand the logic of your chiluk. If when a store only sells treif food, we say people will assume you went in to buy a soda or use the restroom; then kal v’chomer if the store sells both treif and kosher, we should definitely say people will assume you went in to buy kosher, a soda, or use the restroom?
Unless you mean, that the issur is not ‘maaris ayin’ [since one could be entering to use the restroom], but rather causing a ‘michshol’, in other words, someone ignorant might think that since this religious Jew entered the store, it must be an all kosher food store and he will then eat from all the food in the store; hence the difference between an all treif store [which even an ignorant person will not come to err] and half kosher/half treif store?