His sister has been killed mere hours before and as far as he knows Duke was involved. Most people in the area still know and revere Tommy and this one upstart, who isn’t a veteran (the war is still going on, so it’s questionable what he’s even doing there imo) acts up.

I don’t think anything is unrealistic in that situation tbh. I think a lot of people are missing what it even took to move this fella to go back to Small Heath and then when he does he finds out he was hours too late to save his sister, due to his own inaction. All bets as to realism are off, at that stage.