It's essentially a bit of derisive rhetoric that riles up his base but gives a chilling look into how Rubio can view politics as nothing more than an "us versus them" game between the left and right.
You know who also loves playing that game? Keith Olbermann. If you bring his name up, you're pretty much asking to be eviscerated on his show, especially when you question his love for America, and that's exactly what happened.
"Mr. Rubio, you have long behaved like a teenager who has borrowed his father's suit. I think you don't understand this country. I think you imperil this country," Olbermann roared.
"I think your stupidity is an indictment of the educational system in this country. And I'm sure you feel exactly the same way about me. But what I would never claim about you is that you do not love this country. I would never even claim that in your own way you have tried to build it. You have the right to criticize anything you want about me or anybody else with whom you disagree politically."
It gets only more heated from there.