At this point, Raph was operating on pure instinct, unshackling himself the rest of the way, launching off the bed, and staggering over to unshackle his brother.

While Dipper and Mabel and Nico'd been having fun scaring the scientists into defeat, he'd been laying on the table, helpless, watching a horror movie play out a few feet away. After nearly being cut open while still alive.

Without anesthetic.

"Terrified" was an understatement. Right now, he was so far gone he wasn't even thinking straight. It was all instinct, reduced down to: 'Hit anyone that moves that isn't Mikey, get Mikey free, go go go go go -'

Maybe they were little kids but they were little creepy ghosty murder kids. He was a pragmatist, so sue him.