Early goals from Izale McLeod and Gabor Gyepes had put Pompey 2-0 up but Adam Webster's own-goal and Darren Potter's 72nd-minute equaliser stretched the Dons' unbeaten run to six games.
Robinson threw on Smith after just 33 minutes and reverted to an unorthodox 3-2-3-2 formation which sparked the Dons' fightback.
But afterwards he hit out at the officials for failing to protect Smith in the face of fierce provocation.
Robinson said: "We started the game horrifically. We had a decision to make, I was wondering whether it was too soon but I had to make a decision for the benefit of the football club.
"Bringing Smithy on I thought changed the game. I didn't change it, he as a person changed it. I thought Alan Smith should have had a penalty - he doesn't get anything, he is dealt with very harshly and wrongly.
"He has been fouled, punched, spat at and kicked at - it's assault some of the things that happen to him because people know they are going to get a reaction. I got told by an official 'yeah but he's a player that once was in the Premier League who is trying to prove a point'. How can you accept that? I think he's dealt with very differently to the rest and that's what's wrong."
