Silly that the protests are about Japan sending mercenaries and not that those mercenaries massacred a village.
Also, why is the Japanese government responsible for private citizens choosing to work as mercenaries? Obviously there is reason to suspect that that "loophole" could be abused, but in this case the government in fact did not send this mercenary group (as far as we know).
Also, people keep saying "there are no heroes", "it's all grey", "war is hell", etc, but fact is that the author of this manga really went overboard in painting the USN as the "bad guys" (even calling them "genocidal" for attacking a convoy of soldiers, what?). Meanwhile, OCU got off lightly, with a few isolated assholes. What's more, the OCU mercenaries were framed as practically standard heroes in the last arc, despite massacring a village.