The story is not complete and only focuses on how that person spends the money. We should also know not only about how the money is used by that person but also how he is when not gambling. What if he keeps on being a responsible person for their family despite spending money on gambling? What if he can still cover his usual obligations like monthly bills even with a gambling activity?
As a response to the thread's main topic, NO I WILL NOT ADJUST AND GIVE UP MY GAMBLING HABIT FOR THE SAKE OF MY FRIEND. Why should I?
Real friends look out for each other. It wouldn't have been a thing of concern if he was gambling moderately rather he was gambling with a huge part of his salary and still losing. Gambling with a huge part of his salary means he would have little amount left to take care of himself and his family. No one is going to teach him how to spend his money, but a little reminder about his addiction won't hurt. We all know how disastrous gambling addiction can be and I think it is very okay for anyone who truly cares about you to draw your attention to it when you are walking down the wrong way.
If I have a friend who is addicted, I will not quit gambling just for his sake. I'd rather not invite him over whenever I gamble. There are many other measures out there that can be adopted to help an addicted gambler quit gambling or gamble responsibly. If I quit gambling, it will have no impact on his healing process.