salam
Bismillah Hir Rahman Nir Raheem
who ever your friend is, if he is a muslim or non muslim he is entitled to whatever he wants to do. There is no compulsion in religion. If he wants to join a gang he can join any gang he wants.
That goes for any one. When it comes to being acceptible islamicaly, no its not something that benefits us as a Ummah or pleases Allah, and our prophets never joined cults or gangs.
I will not spread bad words about freemasons, as I don't like people with no knowledge spreading bad words about Islam.
Life is all about learning, may Allah guide us and keep us on the straight path.
Salam alaikum