No that’s not true. Gambling has many positive sides.
Smoking and drinking alcohol are also harmful but as long as you don’t overdo them, they won’t destroy you.
Same with gambling.
Like the other bad habits I mentioned, as long as you are in control and having fun, gambling is no different than watching a movie at a theater.
It is full of entertainment if you ask me.
For people who are winning gambling is positive and to those that are losing its negative, this is the mental construct of some gamblers. You can't expect someone that's having a lot of winning streaks to say that there are no good sides of gambling but when the person becomes addicted and starts experiencing the down sides of it then they will know it has a good and bad side. But like you said, it's harmless if you don't overdo it