Interesting proposition that makes a gross generalization, but they'd better solidify that to more than "he was a swinger so his friends did it." In that case, you could use the common perception of Harley bikers to go after the family of any children of bikers murdered
For the record, I was exposed to the biker community through family for most of my adolescent life, and they are generally good people with the usual few exceptions. So don't get on me about the biker reference.