On the other hand, Avanti's Angels messed with the WoB's plans in the Periphery and the WoB pretty much ignored them until the Angels started to take contracts in the Protectorate area after the Jihad kicked off, and even then it seemed to be more of "We're attacking a hostile military unit," rather than "Rawr, kill these guys!"
It might also depend on who the destroyed SF unit was exactly. Apollyon might not care if it was frails, while an attack on the MD might result in murderous and overt aggression.
If it was a WoB Militia unit, or a ROM unit, Cameron St. Jamais might take it personally, or might just consider it a cost of being in the war, rather than "I must dedicate a Division to hunt down some mercenaries that beat us."
Then again, maybe nothing militarily will happen, but your next contract takes you to the Davion Outback where you find yourself right in the path of some ticked-off Snow Ravens.
Or they might be unlucky enough to be jumping through a system where the WoB has a couple of Q-ships lying around.
It all just sort of...depends.