Did the fan do the right thing?
Most definitely he did NOT do the right thing.
In all cases, the BIBLE gives sure and clear guidance:
Leaving aside the many possible explanations for people's behaviour,
including that hey, maybe "Jason" was her brother or son - etc.
We have clear instructions from Jesus the Christ on what the RIGHT thing is.
He should have written the note to the woman, not the man.
We are instructed to confront a brother or sister in Christ privately
when questions, doubts, or inappropriate behaviours arise. (Matt 18:15)
Only when that fails (to expose an explanation or repentence or an end),
are we then to confront that person with a witness, again privately.
Its only on a third pass that we confront such a person openly before
the community.
Now these are instructions for Christians inside their community,
and within that community there is no male or female in terms of
honour or status, so women must be given the same courtesy as men.
But this is a further step away from such action,
because the observer/snitch does not even know if these people are
Christians.
"Those OUTSIDE [the Christian community], God judges." (1st Cor 5:13)
That is, God is the God of the whole earth, and is also God of unbelievers
and God of those of other religions or beliefs, who are outside the
Christian community.
It is not under the authority of ordinary Christians to attempt to
LORD it over unbelievers or police them, except insofar as they
impact on Christian communites.