It's an edit. The original has one guy saying 6, the other saying 9, because the creator naively thought "oh the political divide is really just down to people not understanding each other". This is a fairly common opinion of dipshit american centrists.

The edited version points out how this is incorrect, and that in reality different people have entirely different political views which cannot be reconciled. The example used is that rich people (the same ones that make up the US government and receive bribes from health insurance companies, for instance) want to keep making money from predatory health insurance and so oppose universal healthcare, while the average citizen supports universal healthcare.

It's not. The two people in the picture are disagreeing. The joke is that normally this picture would be captioned with two people simply disagreeing over weather the shape is a 6 or a 9, but instead they're disagreeing with a political position.

Says why right in the picture.

"Fuck them poor people"