It's not debatable, they understand already that gambling is a risky game so they need to accept whatever the outcome.
I have referrals and I believe they are losing but I have not received any messages telling that I was blame because they lose in gambling. Maybe the right person to be blame is themselves.
You are right! They have their own decision to make, they are responsible to know the risk of gambling. Inviting friends to refer has a hard part also, you should have a good charm of encouragement; you need to help them too on how to earn.