It's true that people will always have diverse opinions about gambling, but yet that doesn't make gambling an evil act, as it's just a mere business which involves trying of luck. Hence, if you see people speak so bad about gambling, it's literally a sign maybe they might have lost huge sum to gambling or either knows someone who lost huge sum to gambling. Gambling is not a sin, and can never be an act of demonic manipulation, it's just business, and the earlier these people understand it this way as the primarily aim/concept of gambling, the better for them, because the probability of the casino winning is always higher than that of the gambler, which is why if you lucky enough to win, you could get paid over a $10,000 by simply betting with an ordinary $5.