Monday night was Rick Monday Flag-Saving Bobblehead Night at Dodger Stadium. In 1976, two damn hippies (no doubt the common characterization at the time) tried to burn an American flag on the field during a game between the Cubs and Dodgers; Monday, then the Cubs centerfielder (he later played for the Dodgers), snatched the flag away. Video of the incident is included in the link.
Monday discussed it in a 2006 interview:
“That means something, because this wasn’t just a flag on the field. This was a flag that people looked at with respect. We have a lot of rights and freedoms — not to sound corny — but we all have the option if we don’t like something to make it better. Or you also have the option, if you don’t like it, [to] pack up and leave. But don’t come onto the field and burn an American flag.”
While I have argued that the stands of a ballpark qualify for designated public-forum status, the field itself does not, because speech is inconsistent with expected uses (i.e., playing baseball). So Monday is half-right in that last sentence: Don't come onto the field and burn an American flag. Make sure you stay in a public forum.