Whether or not anyone took them seriously is irrelevant. However, at least one person took it seriously as they recorded video of it.
Any deviation based on color, organiation, etc... is a racist tinged decision. While equal protection under the law was added with the 14th amendment, equal application of the law must also be accomplished NOT MATTER what occurred and I think you agree - they broke the law, but justice was not served and these types of errors by the DoJ further divide this country racially as it appears as though race was a motivation. This prompts you, a black man to say "justice was served" and me a white man "justice was absent". Go back 50 years and the direct reverse was occurring every day. How is continued racism 50 years after civil rights moving us as American's forward? It's not. I didn't own slaves; my family came from what is now Serbia - poor Germans who moved there at the turn of the 19th century were indenture servents to the Yugoslavians and Hungarians who wanted them out and who treated them as dirt. You're baggage and the baggage that is being trotted out by the injustice of this case only serves to divide us as Americans. You should reject it. You weren't a slave, you weren't oppressed (depending on your age) and you have the benefits of almost everything MLK dreamed of during his life. Why take steps backwards? Doesn't make sense.
Let's just say these guys were KKK members, and I'll apply your view to this, and the KKK members were in this locale in Philly --- intimidating black voters. Still okay with your application of what is fair - that this was "justice"? I wouldn't be.