That is despite the fact the Dutchman made a foul-mouthed radio riposte during the Monaco race, when a pit strategy gave his teammate Daniel Ricciardo the track advantage.
Asked if he understood the outburst, boss Horner told Auto Hebdo: “Of course.
“When you end up with your teammate in front of you when he was behind you, you can be angry.
“But once the circumstances were explained, everything was in order,” he added.
Also angry after Monaco was Kimi Raikkonen, amid suspicions Ferrari deliberately disadvantaged the Finn so that teammate Sebastian Vettel could win.
“I don’t think Ferrari did anything deliberately,” Red Bull’s Dr Helmut Marko told Auto Bild.
“He had to react to us and Bottas because he was just too slow. We also had to pit Max early,” he added.
Ricciardo was on the podium in Monaco ahead of both Mercedes, but Horner says that does not mean Red Bull’s 2017 troubles are now effectively over.
“I am worried about Montreal, Baku and Spielberg,” he said. “They will be the biggest challenges along with Monza.
“If we manage to do well on those three tracks, what we have in the pipeline should enable us to have a much better second half of the season.”