It's very simple to understand. Love is better than hatred. Likewise, kissing is better than hitting each other. But doing it delibrately at a place where onlookers of whatever age and sex feel insulted / jealous /embarrassing / bereft of a partner is wrong. Do we like eating at a place where there is hungry people all around looking at us with dazed eyes
In nut shell, must enjoy if you can but don't cause illfeeling amongst others