Did you file a countersuit? I always wonder when I hear about these situations, how these types of scams continue to operate?
Since the other side may be doing this commercially, they may be thinking in terms of mass production. In other words, they file lawsuits and earn as much as they can. If they can't win, they keep filing lawsuits against others. They don't bother.
They might not be making it a matter of pride; they might just be thinking about making money.