In my culture, people around you are categorized into two groups:
1- mahrams: People among whom there is a marriage impediment :all people of your own gender plus those of the opposite sex who are your: parent,siblings, aunts/ancles,grandparents,grand children,spouse,grand aunts/uncles, also your father in law and mother in law. Also every young child and the family who may have nursed you as a baby.
2-not mahrams: People who don't have a marriage impediment with you.
Now, kissing, embracing, shaking and holding hands and even looking at the body of people of group 1 (exluding the reproductive organs) is allowed on the condition that you don't do it in order to get carnal pleasure. (With spouses it is different)
about the 2nd group: one must have head covering and not to touch any part of their body.(unless it is an emergency)
Why are you annoyed at two men kissing but not at 2 stranger man and woman kissing?
Sin can exist in both cases and most of people are heteroes. therefore the latter has more chance of leading one to sin.