Karl Hawley tapped in the only goal of the game four minutes before the break to keep alive the Iron's hopes of avoiding the drop as the Dons' season fizzled out.
The Dons piled forward after the break, but Scunthorpe goalkeeper Sam Slocombe produced a string of fine saves, acrobatically denying Shaun Williams, Luke Chadwick, Dean Bowditch and Mathias Doumbe.
Robinson said: "The first 45 minutes was not acceptable, the way we started was appalling.
"We looked nervous, edgy or like we didn't care. There were two or three free-kicks where we just ambled for the ball like we had all afternoon.
"It's a reality check for a lot of people. I've just said to them in there that it's the first time they've worn the new kit and it will be the last time some of them wear it.
"The energy and enthusiasm wasn't there for 45 minutes - it's not good enough.
"Second half we were alright. We completely dominated the game and probably should have got back on level terms, but the first half has let us all down.
"I'm gutted and it was a bit embarrassing walking round there at the end saying thank you - we've let the fans down.
"If the players have got a problem with me saying that it's not like I really care at the moment. The ones who have got a problem with that are the ones I don't want at the football club."