This has been going on since the late 80s - early 90s with the advent of gangster rap along with the glorification of the mafia and crime/heist movies. Quentin Tarantino, Scorsese, Depalma, etc. It’s really nothing new. I am young enough to still be somewhat in touch with current pop culture and the gang banging stuff is prevalent especially in Hip Hop. You never heard the phrase “Rappers want to be athletes and athletes want to be rappers?”
As far as the rule change, I kind of agree. I can’t stand taunting celebrations. I think it’s disrespectful. What happened to good sportsmanship? If the celebrations are in FUN like Stevie Johnson’s “Why so serious?” shirt or Joe Horn pulling out the cellphone then I am all for it. But some of them are flat out disrespectful like the throat cut, Tyreek Hill’s 👋, and standing over a player after a big hit.