I am confused, they knew it that it is haram but they gamble because they don't see it as a haram. I think these are the people that I am talking about as the blacksheeps.
No need to be confused. That is human. They clearly know that it is haram but they still gamble. That's because the temptation of gambling can make them forget for a moment about the rules of their religion. And they even say it's okay, especially if you win. Apart from that, we also cannot force them to leave gambling because they desire to continue gambling. We can only give them advice and then it's up to them because they are the ones who live it.
Firstly, if you just say and relate to various activities which according to all religious teachings are prohibited and haram then it is clear that many of these prohibitions are violated and are not really cared about.
Not only gambling, but consuming alcoholic drinks, free sex, and narcotics are all prohibited for all existing religions because religion teaches virtue and also the philosophy of living with love for God and carrying out the various recommended religions.
But in reality, many people violate all of this out of mere satisfaction and of course this is mistake if it is judged using religious teachings and regulations prohibiting religious people.
We can only remain good people by not harming other people, even if we do some prohibitions, but if it doesn't harm other people then just do it because whatever the consequences, only we ourselves will accept it.
If you really think it all mistake that needs to be fixed then leave everything behind, never try again to do anything that is clearly prohibited.
We live in modern times and when many religious prohibitions are violated it has become habit that cannot be avoided.
In gambling, we ourselves decide to start and if we can't accept it then just do what we think is right.