The first use and meaning of "gentleman" is number 1 below, which is completely obsolete and out of use for about 200 years.
Numbers 2 through 4 are still in use with older generations today, but are foreign concepts to young people under 30 IMO.
People under 30 today don't (IMO) even know what a gentleman is, but the word still exists and the Andrew Dice Clay joke about it reflects a funny, and possibly realistic new standard of what a young gentleman is today. It's sad, but also funny too. May as well enjoy the laughs where we can.
1) A man who is gentry, nobility (but not royalty), upperclass.
2) A civilized, educated, sensitive, well-mannered man AND he has high social standing. That's a high standard. Probably the standard back in the days of my great grandparents and before.
3) Since lowered to mean any of the qualities of number 2, but no longer requires all of them.
4) A man of good behavior who is considerate of others. This is the definition my grandmother taught me.
5) A modern "gentleman" today is (as the trend continues) held to a lower, ever more modest standard than before.
I'll give a couple examples of a modern day young "gentleman".
Andrew Dice Clay joked that a modern day gentleman is a man who takes the dishes out of the sink before he pees in it.
My girlfriend and I joke that a gentleman always applies lube before fucking his GF in her ass (with or without her consent), and before he accidentally chocks her aka rodeos her.
I'm a mix of old school and modern gentleman. I'm to kind to slap a woman's face or breasts. The idea of such a thing apalls me because it could injure her, and hitting those areas is off limits, even for fun. However, I do love slapping her ass good and hard (with my hand). If she screams and cries a little, that's a great aphrodisiac, but no woman ever got injured from a hand slap on the bottom.
The expectations of gentleman today are so low that I can be a modern day gentleman and an old school jerk simultaneously.
This is all a reflection of society's values in decline, IMO. Such that women my own age think (and tell me) I'm slightly a jerk, while younger women think (and tell me) I'm sweet (i.e. - a gentleman). I treat women exactly the same, regardless of their age. At least until the young women start acting appreciative of my "gentlemanly" ways. At that point I probably do treat them better because they treat me better.
From the point of view of young women, I can see their point. Compared to the typical young male brutes today, I am relatively a gentleman. Even though by old school standards, I'm a bit of a jerk.
The word "gentleman" is in decline along with the rest of society's values. Try to see the irony and humor in things because that makes life easier.