I am sure it is not difficult for you to understand the idea that certain things are more untzniusdig in more insular communities than they are in more integrated ones. Even the halacha recognizes this distinction to some extent. It is all about perception. If you are in a place where it is not normal for people to dress a certain way and you see someone dressed that way, it will probably make you react differently than if you see the same person dressed the same way in a place where it is normal.
That is analogous to what is going on here. Of course, parents and teachers have always been showing affection, and that is a wonderful thing. But each society has its own ways of expressing affection. If you express it in a way that is different from the norms of the society, your intentions might be to express affection, but it will not be taken that way. On the contrary, depending on the circumstances you could cause great psychological damage to the child by doing so. So stick to showing affection in ways which fit the societal norms.