Clearly the players he opposes (who are also millennials) are taking exception to it and finding additional motivation. That's the reason it is being talked about. Allen was angry about it and it's obvious he had been talking about it with his teammates. And the Bengals were also unhappy about it.
So yeah, it was certainly not as big of a difference in games that people are making it out to be, but still. You don't want to give the opposing team additional motivation unless you are prepared to back it up.
And clearly Juju knows it to be disrespectful. He is dancing on another team's logo. I'm sure he isn't an idiot. He knows what that means. He's probably just fulfilling a dare.