As a life-long black guy, I don't mind weighing in...
First off, I appreciate your position as someone for whom a particular negative connotation doesn't have cultural resonance. I also appreciate that you didn't just dismiss cferejohn's concerns but instead asked for an explanation. So, as far as I'm concerned, this is an honest mistake on your part and not an intentional reference or jab.
In the US, from about the 60s onward, a ghetto specifically meant a low-income, underdeveloped part of a city whose only residents were (initially and almost exclusively) black or brown. In your defence, "Ghetto Blaster" became associated with boom boxes because of their prevalence in urban black communities. You think of boom boxes and it's not long before you think of break dancers. So you're not wrong in using the phrase the way you're using it, but keep in mind no one called them ghetto blasters by way of a compliment. Think: "I'm sick of these no-good hoodlums loitering around and blaring their ghetto blasters!" and you have in idea of how the term would have been used.
This, however, isn't the biggest issue.
Unfortunately, especially in the US, racist imagery often equated black people with apes. So, by having apes using "Ghetto Blasters" you've unintentionally stepped into a huge racist trope that for some audiences is basically saying that your game is about uncivilized black people blasting their "jungle music".
Of course it isn't. Of course you're not saying this at all, but this is a deep, racialized historical quagmire. And this particular card coupled with your game's premise has you standing knee-deep in it.