I am no expert on Christianity but doesn't a kiss on the forehead symbolise from vicar or priest symbolise a blessing, just as a polite greeting from an English person might involve a handshake or two kisses on the cheek from a French person. Its all about understanding other cultures or Faiths, and you would have thought in this day and age we could do that!
In my opinion the difference is that this kiss was not done in private or in secret, which most cases of nastiness are done, and children, and parents it seems, should be taught the difference between touching and kissing that is appropriate and that which isn't. I would be interested to know if the child was bothered.
I think we are becoming a messed up society about our kids, I have recently heard parents slating others for letting their little kids go naked on a beach while dressing theirs in little frilly bikinis, and don't get me started on Bratz dolls!