day-trading is part of trading styles that have "blessed but also ruined" people's finances just like any other style of trading
Playing dice is also a kind of trading but with negative edge (core argument). You can argue the same for any casino game with negative EV that some will win and some will lose, but the real question is can you make sustainable income from day trading, answer is NO, the math is not on your side.
Yes, there will be occasional winners with longer winning streak, just like in casino, but overall population will make a perfect bell curve as per the odds (which are not in your favor.)
I understand the school of thought you are driving at but you shouldn't have used trading as a kind of gambling, they are two different things even though they look similar. Again, you asked a question and also answered it yourself, that's funny of you to speak for everybody. If you can't sustain a good result for day-trading, does that mean other people can't? Day-trading may be very risky but it's not the reason why it should be totally condemned.