when is something an insult?

[The Stranger]

And if someone feels insulted, how can that not be called an insult? I say it's a subjective feeling that must necessarily be decided by the one on the receiving end.

Because at the end of the day, people can feel insulted by everything. The clear counter-example to what you just said would be Homophilia and Homophobia. Some people are gay, other people can feel insulted by this, but does it therefor mean that being gay is an insult or is insulting?

Ofcourse when someone feels insulted, no rational reasoning can take away his feeling, but still we can discuss wether his feeling is justified. Similar to fear, sometimes fear is justified and sometimes it isnt, this doesnt take away the fear of one who is afraid, but it can allow us to say that what he is afraid of, is actually not a threat.