Could you explain what the chart means in detail? You are using it to prove a point but I am sure it does that (or even WHAT it does).
It's a chart of first order DW-NOMINATE scores over time. What it basically shows is congressional ideology over time on a constant scale from -1 to 1. 1 is the most conservative you can possibly be and -1 is the most liberal you can possibly be. If you look at the last 30 years or so you'll see that while Democrats have moved to the left slightly (about -0.1 or so) to a -0.4, Republicans have moved hugely to the right (about +0.35), up to about a 0.6 now (the chart is a few years out of date). So while we are in fact polarizing as a country, the vast majority of that polarization has come from conservatives moving farther right, not liberals moving farther left.
So when people like GagHalfrunt try and say that both parties are polarized and both parties are the same, he's actually playing right into the hands of the extremists running the Republican Party right now. If they can convince people that the Democrats are just as guilty as they are it legitimizes what they've done.