Your friend is quite some dreamer if he can thinks that he can predict gambling bets. Of course he maybe right if he wants to hack the MD5 Hash of a single spin but casinos are bit forward of him. They only leave a seed of MD5 to verify for only a few minutes so no chances to hack such things. Bitcoin so far in its 7 years of life is not breached in security. All the cases of hacks and steals is because of user fault. So bitcoin is as strong as it can be.
there are allot of people who dont even know what to do with the bitcoin. But there are so many things to do with the bitcoin you cant imagine so he is really strong.