There's a few that are springing to mind for me.
Ex champions who carried themselves with dignity and pride when holding the belt, but when they lose they go full bitter attack online!
ALDO - Greatest FW of all time, great champion but .... He lost in dramatic fashion really quick to Conor and then when Mac lost to Nate, Aldo turned into a baby online calling him a pussy and other stuff
ROCKHOLD - Won against the best Weidman in his prime, was gracious and then when he lost to Bisping, turned sour and lost all humility online and more so at the post fight presser
WEIDMAN - The American Dream, beat the GOAT, carried himself with class and respect ...... Lost to Rockhold and called names online and now more so is doing the same to Bisping trying to trash talk himself a title shot 
Weidman didn't carry himself with dignity and pride. He used to call out Anderson all the time and talk about how he would beat him king before his title shot came. Rockhold did the same before their fight, and Chris got all pissy about it. 
Cos Mac has them all thinking they need to talk shit to get over these days. Sad.
They've seen McGregor talkin' shit and getting paid big bucks, and they'd like some of that.
Dodge135 -Unfortunately this. After Chael and Conor, people learned you have to talk a bunch of shit to get the good fights and money.They've seen McGregor talkin' shit and getting paid big bucks, and they'd like some of that.
Chael created the blueprint by being witty, but in such an advanced way that it was impossible for an intelligent person to take it personally. Unfortunately, these young fellows have missed that delicate balance, mostly because they aren't clever enough to strike it.
The sight of Bisping with the belt scrambles their eggs, turning them into immature, gibbering, salty wrecks.
Bisping is awesome.
Outlaw'd by Lytle - The sight of Bisping with the belt scrambles their eggs, turning them into immature, gibbering, salty wrecks.
Bisping is awesome.
Not quite, they still see the belt Bisping is holding as the easiest belt to get their mitts on in the UFC. Expect to see more fighters heading towards 185lbs while Bisping is on top.
Dodge135 -Bisping moving up to 205 according to my local farmer.Outlaw'd by Lytle - The sight of Bisping with the belt scrambles their eggs, turning them into immature, gibbering, salty wrecks.
Bisping is awesome.Not quite, they still see the belt Bisping is holding as the easiest belt to get their mitts on in the UFC. Expect to see more fighters heading towards 185lbs while Bisping is on top.
Dodge135 -Except Conor didn't talk shit after his lossThey've seen McGregor talkin' shit and getting paid big bucks, and they'd like some of that.
He got serious about the rematch to the point of being bumped from 200
Not sure if "sour" is best co-relation to McGregor losing and the examples from OP
Outlaw'd by Lytle -Dodge135 -Bisping moving up to 205 according to my local farmer.Outlaw'd by Lytle - The sight of Bisping with the belt scrambles their eggs, turning them into immature, gibbering, salty wrecks.
Bisping is awesome.Not quite, they still see the belt Bisping is holding as the easiest belt to get their mitts on in the UFC. Expect to see more fighters heading towards 185lbs while Bisping is on top.
That's not a bad strategy, get more big money, no risk fights without having to retain his belt.
Rockhold was, is, and forever will be a douchebag. That isn't anything that just happened.
Rabid Bunyip -Dodge135 -Except Conor didn't talk shit after his lossThey've seen McGregor talkin' shit and getting paid big bucks, and they'd like some of that.
He got serious about the rematch to the point of being bumped from 200
Not sure if "sour" is best co-relation to McGregor losing and the examples from OP
But he did dodge UFC 200.
Suspiciously Official - "Everyone is trying to be like Connor."I'm gonna be "that guy" for a second...
Conner got it from Chael.
Chael got it from Pro Wrestling
Pro Wrestlers got it from needing to make their product more entertaining in the 80s when the second wrestling boom hit and had to appeal to television audiences.
Pro wrestling always had the promo. It's how they got paid- putting asses into seats. Even Muhammad Ali cited Gorgeous George as an inspiration for trash talk. Interviews weren't merely interviews, it's how they sold themselves to the public. When they were good the public would pay to either see you back up your words or to get your mouth shut. It's an art form.
Chris is a douche
2JupitersTooMany - Chael created the blueprint by being witty, but in such an advanced way that it was impossible for an intelligent person to take it personally. Unfortunately, these young fellows have missed that delicate balance, mostly because they aren't clever enough to strike it.Great fucking point! Honestly, nail on the head right there. Vu
Suspiciously Official - "Everyone is trying to be like Connor."
Conner got it from Chael.
Chael got it from Pro Wrestling
Pro Wrestlers got it from needing to make their product more entertaining in the 80s when the second wrestling boom hit and had to appeal to television audiences.
Conor got it from Mayweather though. He also projects a lifestyle that you either envy or detest. Makes him far more polarizing than the simple trash talker.
Don't think Conor looked at Mayweather at all
Ken Shamrock is the king of bitter. Don't get me wrong i love ken but he seems to miss the old days so much he's started to hate them
Decreased testosterone, increased estrogen = USADA.