skyrideIt's just people being excited. If you actually think about "let's go yankees", its actually a totally meaningless statement, but tons of people say it and just rolls of the tonuge really easily when you're excited because it's only like 4 syllables. It's like the irl equivelant of CTRL + C CTRL + V.
"Let's go yankees!"
Go where? What are we doing there? How are we going to get there?
Now you're just grasping at straws. If you're seriously going to pick apart "Let's go <x team>, let's go", a common rallying chant, completely out of context your argument for this memespouting business is incredibly flawed. In fighting games you can have people just going completely apeshit going "OH! OH! OH! OH!" every time a gigantic combo is unleashed or you'll have people spamming pjsalt in chat on twitch and THAT MAKES SENSE. Salty is a common term used to describe someone who is bitter about losing a game, and there are times where people are just biblicized when they're in the lead. They get straight up demolished. Cue the chat throwin' down pjsalt in the chatbox because I'd be salty too if I had a big lead and I got completely outplayed.
Even putting "raise your dongers" in context to the game doesn't make any sense. It's not a cheer, it's not a jeer, it's not a proper exclamation - it's just some stupid infectious league of legends in-joke.