Bautista's moment in the playoffs was special; the playoffs, THAT crowd, everything on the line. It was a very intense moment. I don't think he was doing that to show up the pitcher, but rather, to release exhilaration from coming up huge when his team needed him most. I have absolutely no problem with that. It was awesome to watch.
It's when guys start taunting opposing players or do some ritualized dance to pander to the audience that gets annoying. Everyone's "selling their brand" in sports these days. Aaron Rodger making TV spots out of his championship belt taunt. Colin Kaepernick legitimately copyrighting the term "Kaepernicking". They're not spontaneously doing these out of exuberance; they're meticulously planning it in order to get endorsement deals. Pretty lame. If I want to watch some narcissist beat their chest and sell me merchandise I'll watch pro wrestling(and I do...it's great!).
The "unwritten rules" thing is in place to keep some of the egomaniacal behavior at bay because....NO ONE LIKES THE GUY THAT SKATES BACKWARDS AT THE ROLLER RINK! I digress...
Does it get tiring to hear traditionalists preach the unwritten rule as gospel? Sure. It's like your grandpa telling you not to do something. You still want to do it. Maybe you want to do it more so now out of defiance. I think that's where the Harper interview comes in to play. A young guy who plays with fire getting told to cool his jets because it's not the prototypical old timey baseball way. He's lashing out now and trying to break the prototype. Goose Gossage is just being an old crow. Nothing to see here...
I will say this. I always cringe when I watch an interview with a young player and you can tell they're making a concerted effort to hit buzz phrases like "playing the game the right way" or "play with humility". It's like they're reciting lines that they've memorized from the unwritten book of baseball cliches. Yuck.
The 2015 revision to the unwritten rule should just be "Have fun but don't be a d**k about it."