Correct. Kepler getting the glove on that specific ball makes it an error. Just touching the ball with the glove does not make an error, like a diving play or something. A base runner cannot, by rules definition, cause an error. That's called interference.
From MLB.com
Definition
A fielder is given an error if, in the judgment of the official scorer, he fails to convert an out on a play that an average fielder should have made. Fielders can also be given errors if they make a poor play that allows one or more runners to advance on the bases. A batter does not necessarily need to reach base for a fielder to be given an error. If he drops a foul ball that extends an at-bat, that fielder can also be assessed an error.