You're holding up a massive straw man.

A C&D like this is pretty standard fare between competing businesses. If you sell widgets and WidgetCorp sells widgets, you are completely allowed to try and poach their customers, but WidgetCorp is allowed you prevent you from doing that in their store. Furthermore, if the accounts were specifically created for this purpose it's a clear violation of the TOS and there may potentially be damages there, or even possible criminal charges (thanks to the wonderful CFAA - ack).