>>130981554>And Sonic himself seemed to think that he had gotten over it once Fiona betrayed everyone for Scourge, which obviously wasn't what happened, but he had no way of knowing that
The very first issue he saw Sonic with Fiona he yelled "I HATE YOU" and ran off on his own weeping in misery.
He was miserable and in-tears for the entirety of Sonic's time continuing to date Fiona despite how obviously it was affecting Tails. See: the Shadow origin issue
Tails was the one most badly hurt and humiliated by Fionia betraying everyone. See: the Slap and him weeping again afterwards and running off to be on his own
Tails continued to be hurt long afterwards, and voiced this fact to Sonic's face. See: Antoine's wedding, where he literally said out loud how miserable he was about it. See: 175, where literally only Rotor even bothered to care about the fact Tails was obviously depressed, and Sonic and Sally were too busy sniffing their own farts.
TL;DR Sonic has utterly no justification. Sonic knew Tails loved Fiona, Sonic knew Tails was humiliated and heartbroken by everything Sonic had done regarding Fiona. Tails voices this fact to Sonic again and again and again.
End of the day either Archie Sonic is a braindead 50iq brainlet with a learning disability that prevents him from making even the most obvious of social observations, or a spoiled narcissistic manbaby who doesn't care about his "friends" beyond getting them to worship the ground he walks on and who didn't get beaten nearly enough as a kid. Chances are it's the latter.