The big argument against it is that it shows up the pitcher that they just got a big hit off of. That it's disrespectful. If that's the case, then why is it okay for a pitcher to show up the batter when he gets a strikeout? Why is it okay for the pitcher to pound his glove or hop off the mound when he gets out of a bases loaded jam? Doesn't that show up the batter? There is no retaliation if a pitcher shows up a batter is there? It's not like a batter can chuck his bat, helmet, or batting gloves at the pitcher. But batter beware if you flip your bat after hitting a 435 foot home run to take the lead in a game. The next pitch might find your rib cage.
It is not disrespectful to the pitcher. These players are human, can't they show some emotion? A little bat flip or bat toss isn't the end of the world. If you think Jose Bautista or Bryce Harper doing a little bat flip is outrageous, search 'Korean baseball bat flip' on YouTube. Let me tell you, these little bat flips will seem tame. The big controversy last post season was Jose Bautista. Everyone knows the bat flip. But did they watch the game? Did they see Texas take the lead in the top of the 7th? Did they see the emotions start to amp up? The reason for the bat flip was because the game was so tense and that home run gave the Blue Jays the lead again. Emotion is allowed. They are human. But you had players coming out of the woodwork saying that Bautista was disrespectful and showed up the pitcher. He had been around for a long time and is a respected player in the game. This was his first postseason series and you're telling me that Jose Bautista cannot show emotion at that point? Now, if he does this every single time he hit a home run, you might have a bit of an argument. But when he hits home runs, he puts his head down, runs the bases, and celebrates with his teammates. There isn't jumping up and down in the batters box, there isn't any staring down the pitcher. In my mind, He has earned the right to bat flip.
In football, you see small celebrations all the time. Probably twenty times a game you see a guy stand up and signal first down after a big play. Is that showing up the defense? Not really. There are celebrations in the end zone after touchdowns. The NFL has worked to curtail excessive celebrations with the entire team dancing for an extended period. But it's fine if a player does a dance or spikes the ball. In basketball you see players flex their muscles and let out screams after monster dunks. You see them throw up three fingers when three pointer is scored? Is that showing up the opponent? Not if they flex their muscles and then turn around and go back to the game. If they stand above them and stare them down, that's taunting and maybe a foul? I'm not sure. Everything seems to be a foul in basketball. In hockey, there's small celebrations. Nothing major unless the team wins a playoff series. But you still see some celebratory jumping into the glass after a goal. Or going down and touching the ice as they skate away. That doesn't mean the player is going to get slashed or punched in the mouth the next time he is on the ice.
It's funny to listen to older players talk about how there weren't any type of antics back in the day. Oh really? There's pictures and video of Mickey Mantle bat flipping after home runs. Babe Ruth calling his shot isn't showing up the pitcher? If that isn't showing up the pitcher, I don't know what is. He was saying 'doesn't matter what you throw, it's leaving the park'. Was there outrage when this happened? Pete Rose ruined Roy Fosse's career in an All Star game by running him over to score a run. Is that not disrespectful? It was an exhibition game. There is photographic evidence of Al Kaline doing bat flips. Who cares? We are all human, we are allowed to have emotions.
I think that there is a fine line though. If your team is down 8-1 in the 9th inning and you hit a solo home run and bat flip, that's neither the time nor the place. If you stand in the batters box watching the ball sail over the fence for an extended period of time, that's showing up the other team. Especially if it's a no doubter. If it's close to the foul line, I understand that. But more often than not, the players can tell if it's leaving the park. There is a time and place for everything. And knowing that is part of being a professional. I think asking players to keep their emotions in check every single moment of every single game is asking a bit much.