Perhaps we need Zweiblumen to chime in on the orientation of the gangers vs. the team vs. the area to be protected. I had the opposite image than the one described by rednblack. So, Zweiblumen, are the Chulos currently headed/pointed toward the area we're to be protecting or away from it?
Knucks would counsel that this is the opening salvo of sound and fury that's to be expected of gangers on or near their home turf. It's posturing and a threat display. As the ganger ended with a question (who are you and why should I care) it seems like a natural invitation to explain who we are and why he should care.
Per Knucks earlier post, he would recommend appealing to their profit motive and/or their sense of ambition. Lay out the proposal - that there's more money to be made in an alliance than a war - make them think it was their idea, and let them take credit for it with Two Tooth. That will make them look good to their boss and put some more nuyen on their credsticks in the future.
But if they don't like the sound of that and are just looking to rumble, well then Knucks can oblige. (Logically he understands that it makes more sense to team up with the Chulos to beat down the teenage Technoids, but the Chulos are right there right now and are so conveniently available!)
