The 'experts' in the State Department were having the vapors, and media mavens NBC/ABC/SeeBS were aghast at that damn stupid cowboy for offending the Soviets.
Nothing much has changed on that front in all these years.
Peggy Noonan covered this speech quite a bit in her book “What I saw at the Revolution”. Reagan put that line in himself. The State Dept., etc. kept taking it out (the speeches get reviewed by a BUNCH of agencies, sent back to the speech-writer, the President, then back for reviews, etc). Anything the President says becomes “official” policy, so EVERYONE is real touchy about the contents.
He was handed the final, approved speech on his way to the gate. He wrote in his line, yet once again, in the limo just to make sure he didn’t miss it!
The actual fall of the gate has an interesting story too. Seems a report in the media stated that the East German government had decided to open it up, and would be working out the details in upcoming sessions. But people started showing up at the gate, and the guards at the gate didn’t have all of the details - just that “a decision had been made to open the borders”. So they opened the gate!