The most infuriating aspect of the revelation of Daisy's affair with Gatsby, to Tom's way of thinking, was the realization that Daisy knew Gatsby long before she became acquainted with him. Tom can't understand how they became aware of each other, can't accept that there might ever have been any feelings between the two of them, and becomes livid when Gatsby suggests that Daisy always loved him, even when she was going through the motions of marrying Tom. He refuses to accept any possibility that this story might have any truth to it and is determined to force everyone present to understand the truth of his love for Daisy and hers for him alone.
I can't speak about what happened five years ago because I didn't know Daisy then...But all the rest of that's a God damned lie. Daisy loved me when she married me and she loves me now.