Historically in our younger days, we will bite a mango or something putting a cloth over it , bite and pass on the rest. This was called Kaakkaai kadi. Do you recall on your marriage day, both of you exchanged food from each others mouth ? You feel feed because the people were not sharing solid things like mango pieces etc. So, if the participant do not fedl bad, outsiders have no right to comment on it. For example, you have the right to say, sorry I am not into it. I said once to a family that I will not the dhal because they put the spoon in it after sucking on it to taste the dhal. They understood and I ate other things. Problem solved. But within their family it was OK. Mother use to feed a bite from her food to her child and we have no right to object to it. Each family has own standards. In an Iyengar's marriage, the house lady told me, De, put a red central namam and eat. She really loved me even though I was not an Iyengar. When the food distributor asked me, are you vadagalai or Thenkalai, I said I am nadukkali and he went away. But he dispersed kootu with his hand (that was not solid banana curry, rather liquid type), so I discarded. I did not make a big deal about it.This is a fairly common scene in Chennai and possibly in other progressive societies in India.
Three friends A, B and C go to an ice cream bar and order 3 cones - chocolate, butterscotch and strawberry. A licks the chocolate cone a few times and then passes it to B who does the same with the butterscotch before passing it to C who completes the cycle by passing his/ her cone to A. The cycle repeats for as long as there is some ice cream left.
I did not have an orthodox upbringing but I get a deep feeling of revulsion merely seeing this. I feel the (traditional) observance of Echchal makes all the more sense in these modern times.
My point is all are God's children and your values are in no way above their values as long as it is abusive in nature.
But you have the right to feel the way you fell, but sharing is not your right as it amounts you are expecting affirmation form others about your irrational view.
Do you wash spoons and forks when offered as a guest before using them?