Eric McErlain writes:

Let me preface, I’m a lifelong Mets fan, and no fan of Pete Rose. As far as I’m concerned, he has no place in the game of baseball.
But when it comes to the Harrelson incident, I clearly recall reading in the 1974 Mets yearbook that Harrelson conceded that he actually caused the fight. Harrelson made the admission at a dinner with New York sportswriters where he presented Rose with a “Good Guy” Award.

I’ve been looking on the internet for some confirmation of this. I found this quote from Pete Rose:

I ain’t no little girl out there. If a guy hits me, I fight back.
Reds all-star outfielder Pete Rose
On his fight with the Mets’ Bud Harrelson during the NLCS that nearly incited a riot in Shea Stadium. October 1973.

Of course, there’s this from MLB.com:

In Game 3 of the 1973 NLCS, the Mets take a 2-1 lead in the series by whipping the Reds, 9-3. However, the highlight of the game occurs in the top of fifth inning when Reds outfielder Pete Rose and Mets Shortstop Bud Harrelson come to blows after Rose elbows Harrelson in the face. In the bottom of the inning, the Shea Stadium crowd showers Rose with debris. Willie Mays, Tom Seaver and Rusty Staub are finally able to calm the crowd.

You can read Eric McErlain’s blog, Off Wing Opinion here.