I can see that he would be. While he had a small "on-screen" role, in many ways, he's the linchpin for Tony. He's the bridge between Tony's past and his future and his reaction could have been devastating for Tony and drastically set back his healing. Having his father *FINALLY* believe him and be horrified and rejecting Roy over Tony made, IMO, Tony's eventual progress possible. Boy 43 *needed* his dad to love him and accept him and, most of all, believe him.