You can't convince him. You can tell him and your reasons for thinking he is not a good friend but ultimatly he must make up his mind.
The English phrase "Pray for your friend" is translated to Spanish as: "Reza por tu amigo/a." (male/female friend)
Suggestion: Convince them to do something more fun to them then runescape.
I'll pray for your friend and his dog.
He gives him chocolate
give them space and pray
pray
say please
you tell them to join
What arguments would you use to convince a friend that the lives of human beings are dependent on solar energy?
Your friend is going to see what they want to see; so all you can do is try to convince him the best you can. If he doesn't see what you see then you will just have to let him come around to it on his own.
motivate the importance of that particular download