This person is down and out. OG comes along and insults the guy for doing something he did himself:
Losing tens of thousands of dollars that doesn’t belong to you is dumb on a level I have difficulty comprehending. It is possible that without a loving and wealthy family OP will be made a Darwin victim. As they say, play dumb games and win dumb prizes. Gambling borrowed money has to be expected to turn out like this.
First, it's good advice, and anyone can issue it. Second, true or false (what you claimed of him), the best person in the position to advise in such a situation is the person who has experienced it and now sees it as indeed dumb.
Is narcissism a requirement to scam, or is it acquired after successful scamming?
It's of course after the job is done. But such should also do well to feel like a villain.