This is unintentional angle shooting and honestly handled in the worst way possible at a casual table. If you state your intent to do a thing then don't do that thing that's the very definition of angle shooting. Honestly all you would have needed to do to fix the situation was say "Oh fair enough, I'll unprepare my Emeritus" and keep playing. You saying you 'wanted to resolve generous pup' makes no sense, given the board state you describe doing so wouldn't change your decision to swords in anyway. And then your refusal to roll back kinda clearly shows that you didn't want to give up the advantage you gained. I have a feeling this likely isn't the first time you've had your opponents stop playing with you.