Who can blame him? Biden knows that some people are irredeemable. Ron Johnson is one of them: Over his 36 years in the Senate, JOE BIDEN took pride in establishing friendships across the aisle. And now, as president in a hyper-partisan time, he often waxes nostalgic for the old days and states aloud just how much he likes many Republicans, including Minority Leader MITCH MCCONNELL. But Biden’s love of bipartisanship has its limits. The president clearly detests some on the opposite side of the aisle. There are those he views as convenient foils, allowing him to draw a distinction between his old GOP pals and the new crop of “MAGA Republicans” who, he often argues, pose a threat to the country. Biden frequently seizes on Florida Sen. RICK SCOTT’s plan to cut spending, including putting Social Security and Medicare on renew-every-five-year plans, as a cudgel with which to bash the GOP. There is little love lost between the two men. But Biden holds real antipathy for one Republican above all others: Sen. RON JOHNSON. The president’s distaste is so strong that aides recall him expressing joy at MSNBC host JOE SCARBOROUGH’s frequent description of the Wisconsin senator as having “rocks in his head.” Biden’s disdain for Johnson was evident during last week’s post-State of the Union stop at a union hall not far outside Madison. Reading off a printout, Biden turned to the audience of hardhats: “By the way, you have Senator…” he said before pausing for a beat. Biden smirked. He cleared his throat as…