End up shooting someone and the DA brings up you are in a "gunfighter" club. And we all know that gunfighters were the bad guys in westerns. So he has already built a mental image against you in the mind of the jury.
Yeh, if Ramzi Yousef escaped, broke into your kids bedroom and you shot him just before he sank a knife into them you'd be thrown in jail by a rogue DA because you had a membership to the Gunfighter Club and a Doodie member to boot, may as well plead guilty and beg for the electric ride. Plus they'd double your death penalty if you used reloads or a gun with a provocative name like Cobra.