Baldock twice put the Robins ahead, but fine second-half finishes from Patrick Bamford and substitute Samir Carruthers maintained the Dons' unbeaten record.
Robinson said: "I'm disappointed with the result because I thought we were the better team overall.
"Obviously Sam is going to get all the plaudits, but I'm disappointed with his goals and how we defended them.
"We had 24 hours to put that back-four together, but it's frustrating that our goals have to be wonder-goals and then we gift the opposition goals.
"Sam said to me after the game 'football is unfair sometimes' - I think he knows it was two sucker-punches with his goals.
"But he's a great kid, he's one of our own, but he's done us over.
"If they can keep him fit they will be challenging.
"I told the boys at half-time it was boring - we just couldn't unlock the door and it was a stalemate.
"But second half we were the only team trying to win the game.
"The football that led to our goals was tremendous and the finishing was phenomenal."
Aden Flint headed against the post for City before Baldock put them ahead, controlling Bobby Reid's pass in the box to lash a fine strike into the top corner.
Bamford equalised for the Dons seven minutes after the break when he raced on to Luke Chadwick's pass and drilled a clinical shot inside the far post.
Baldock restored City's lead in the 66th minute when he ran clear on to a long punt and drilled the ball low past David Martin for his fifth goal of the season.
But Carruthers made it it 2-2 just three minutes later, firing an excellent first-time shot into the top corner from substitute Dele Alli's pass.