What is gentlemanly about sex with people you aren't involved in a relationship with?
In today's protocol, I would answer "how you conduct yourself" to that question.
Given how often alcohol is involved how many young men are 'gentlemanly' about such things today?
Pretty impossible to answer that question.
The whole concept of 'gentleman' seems old fashioned and quaint in an era decades after the idea of holding the door for a woman began to be sneered at as sexist and paternalistic.
Which is why I use it purposefully and only partially ironically. Protocols signal virtue in times of low virtue, right ?