An act that bodily commits a person to a terrible conflict, through a transformative or unforgivable act that makes it impossible for the one who "eats
red flowers" to back down from the conflict. Examples of
red flowers may include acts of violence, but could also include "Fighting Words", offensive speech that clearly and unambiguously expresses an intent to fight.
It's an idiom from the foundational
indie game, Cave Story. Within Cave Story, Any mimiga (rabbit person) who ate a local variety of
red flowers would turn irreversibly into a violent
monster. There was some implication that the warriors of the mimiga took highly diluted infusions of
red flowers for strength, but even they took great care not to
go too far. A mimiga would only knowingly eat a red flower once they were ready to die fighting.
"There's no point in engaging with them. They've eaten the
red flowers. (They've tweeted some really stupid and offensive things that they're not going to want to ever have to acknowledge they were wrong about, so they wont, so we can't reconcile)"
"No Averill, don't shoot a partridge in the lord's private hunting grounds. If he finds out he'll deploy his
army and try to evict us."
"Let him. We peasants are ready to revolt, and we'd
win. I'm going to do it, Barclay, sooner or later I'm going to
eat the
red flowers."