Kapler wrote this week he'll remain inside the Giants' clubhouse while the national anthem is being played before games. La Russa believes in the cause just not Kapler's actions.
"I think he's exactly right to be concerned ... with what's happening in our country," La Russa said before his team hosted the Cubs on Saturday night. "He's right there. Where I disagree is the flag and the anthem are not appropriate places to try to voice your objections."
Nineteen children and two teachers were killed at an elementary school in Uvalde, Texas, on Tuesday. Shortly thereafter, Kapler penned an article explaining why he can no longer stand outside while the anthem is being played, writing he's "not okay with the state of this country."
"When I was the same age as the children in Uvalde, my father taught me to stand for the pledge of allegiance when I believed my country was representing its people well or to protest and stay seated when it wasn't," Kapler wrote. "I don't believe it is representing us well right now."
La Russa reiterated his respect for Kapler's intentions but thinks his form of protesting is disrespectful to servicemen and women.
"Some of their courage comes from what the flag means to them and when they hear the anthem," La Russa said. "You need to understand what the veterans think when they hear the anthem or see the flag. And the cost they paid and their families. And if you truly understand that, I think it's impossible not to salute the flag and listen to the anthem."
Meanwhile, many of Kapler's other fellow managers are offering their support for his decision.
Texas Rangers manager Chris Woodward said Kapler's action was "brave."
"I think we're all frustrated, especially in this country," Woodward said. "Nobody's happy. It's not about which side you're on. It's just we've got to get better as a society. ... I'm not going to really make comment either way on whether I would or wouldn't do what he did."
Boston Red Sox manager Alex Cora said Kapler, his former teammate, has been vocal about several subjects and "for that, I'm proud of him. He's a good friend of mine and the kind of guy I respect from afar for what he's doing, and if this is what he's doing, good for him. I understand his reasons. He was very open about it and I know there's a lot of people that are going to support him."
New York Mets manager Buck Showalter also said he respected "how Gabe feels and the way he's going about it." Asked about Kapler, Philadelphia manager Joe Girardi responded: "That's Gabe's decision. That's all, I'm going to leave it at that."
Washington Nationals manager Dave Martinez said he's rarely on the field for the anthem because of meetings and other pregame prep.
"If I'm not out there it's not because I'm boycotting anything," Martinez said. "But I do believe that we need to figure something that's better for everybody's lives because what we have now is not working at all.
"Everybody has their own views and preferences. ... Gabe's his own person and Gabe does what he wants to do. I do things differently than Gabe."
Arizona manager Torey Lovullo called Kapler "a humanitarian," and that he was "very supportive of what Gabe is doing." But Lovullo said he tries "not to get involved in that arena. It's a very, very sad and touchy subject for me."
Los Angeles Dodgers manager Dave Roberts said Kapler "is very passionate about things he believes in and that's his way of protesting. ... I don't think any of us are happy with what's going on in our country. I do respect people using whatever platforms they have to address that."
The Associated Press contributed to this report