Since the sultry obomination race sees fit to continue to embrace expansion into your legitimate backyard, I would suggest that you call upon any alliances that you may have to declare a joint venture into showing these obscure and misinformed malcontents the error of their misbeguided endeavors.
(I would also send in plague bombs in cloaked ships to his core worlds/steal some of planets,
and just give him an old fashion thrashing)
just some ideas mac