I think it is misleading to see "gangs" as being primarily motivated towards violence by retribution for insults--following some "code."
I think that the reality is that when "gangs" are examined more deeply they are in fact found to serve as end-user distribution chains for precisely the kind of product that the Rhodens were involved in. Gang killings have far more to do with economics than ego. They are about protecting turf, sales turf, and reining in lower-level members who may be tempted to "go it alone," or skim profits or fail to deliver with cash in a timely fashion when product is fronted. I don't say this to in any way minimize the deadliness of gang behaviors--only to point out that it is less random than many suppose.
And every teenager who pumps their ego by flashing gang signs is not capable of pulling in back-up or fire-power.
I cannot rule out a gang involvement in this killing--because I have no clue as to how the Rhodens were distributing their product. Whether they were dealing with gangs in cities, or if they had a Mexican connection providing transport, etc. But I don't see that kid with the Facebook beef as being central.
What I do wonder about, however, is the specific event that led up to the FB rant. It sounded as if some of the Rhodens were "protecting" some turf--driving out folks (like that kid) who by chance or intention were driving by.