Guren had been on the battlefield all his life, he faced demons, monsters, and others human alike and not without consequences as his scars could prove.
More than anything he had the strength and wisdom needed to come back each time with a victory or his life and that of his man.
He had learned to use his head as well as his body, so there was a reason behind his actions other than what Thirteen could understand.
Guren was the kind of guy that was surrounded by people willing to follow any and all his orders; mostly he was the one that made them into that mindset by example, training, and punishment.
The outright disrespectful and challenging behavior of Thirteen wasn’t helping him to put his mind at ease, worse it was damaging a person he was supposed to protect: Sinalta, the very princess for whom he formed a female-only knight unit.