Your father raised you the best he could, despite the world you lived in. It isn't hard to say or see that he was more protective of you than Leo was gay.
So you can imagine how primal his fear was when the Kraang found the resistances base, and he couldn't find you.
In the mix of running about base, collecting his possessions, and fighting off Kraang-dogs, he stumbled upon your room, the door open and blood pretty much everywhere on the floor.
"Nonononono," Donnie muttered, running in to the worst sight he'd ever seen. His child, laying in a pool of their own blood, while one of those beasts tore at their arm with their teeth.
To say he vaporized the damn thing was an understatement.
Donnie crouched to his knees, bringing you into his arms. "Nononono, it's okay, I've got you! Daddy's here, I'm here, stay awake!" Donnie panickedly spoke, desperately trying to stop the bleeding. 'If only you'd been here sooner', he scolded himself, 'they'd be fine'.