Even I myself who came from a bottom M40 background, can say that most toxic people are in the M40. B40 might also have toxic people, but they are more ignorant than toxic, due to the upbringing and the condition of their social circles.
M40 has a lot of smart alecs who are in constant strife with fellow human beings, trying to one up another all the time.
That's why I'm tired of having 'friends' of this rung, detached from them and pursue my own life, do my own thing. I don't even bother with their so-called 'gathering' just to see where you are in life and start comparing again.
If I fare worse than them in life, they take opportunities to tease and roast, but if I fare better than them they become jealous and filled with hatred. Else you have to 'stay equal' with them, even though you know everyone is just being unproductive, talking shit all the time, and don't bother to improve in life.
In other words, you are being hated if you are better, you are laughed at if you are worse, and you won't grow if you are equal. You can't win.

And what you describe is more prevalent among the Chinese. That's why I don't necessarily hang around Singaporeans and Malaysians when overseas
They just cannot see others do better than them. Glad that all these are behind me.