For them, everyone is a white supremacist terrorist that does not fall in line, including grannys that stepped inside the capitol.

You, yourself, said it: "why would they have the 'white supremacist' kill the white guy...?" Lots of people would be asking themselves the same question because, on the surface, it wouldn't make any sense. But, if we were the govt/media, we do have a fortunate quote from Biden back in 2015:

Folks like me who are Caucasian, of European descent, for the first time in 2017 we’ll be in an absolute minority in the United States of America, absolute minority....Fewer than 50% of the people in America from then and on will be white European stock....That’s not a bad thing, that’s a source of our strength....It is the ultimate source of our strength, it is the ultimate source of who we are, what we become....It started all the way back in the late 1700s. There has been a constant, unrelenting stream of immigration, not in little trickles but in large numbers.”

Right now, there's a giant horde of Hondurans who are making their way north to invade the US. Any alphabet in DC with a mind to assassinate Biden will immediately blame a "white supremacist" avatar, and find their patsy (just like the CIA did with Lee Harvey Oswald...hey, old tricks are the best tricks). And, as for the "reason" he did it, the govt/media will say that the shooter saw Biden as a "race traitor" who'll let millions of non-whites into the country so as to overwhelm the white demographic.

Here's what'll really bake your noodle: any assassination of Biden will be used as a 'Reichstag Fire'-event that the govt/media will then use as a convenient excuse to begin draconian restrictive measures against whites only because the entire race will be labelled a 'terror threat'. Following that tacit 'green-light', the govt/media will systematically overlook any minority actions taken against whites; and, any attempts by whites to protect themselves will be labelled as proof of their racist, unhinged, radical, subversive, and dangerous 'natures'. Then, as a so-called 'threat to national security', the govt/media will then have the convenient excuse it needs to begin concentrating whites and subjecting them to re-education, and worse. I didn't just make this up; it's directly out of the leftist playbook. They need scapegoats and they need plausibility/justification narratives...even if they have to engineer 'em to happen.

Read:

Rummel, Rudolph. Power Kills. (1997); Lethal Politics: Soviet Genocides and Mass Murders 1917–1987. (1990); China's Bloody Century: Genocide and Mass Murder Since 1900. (1991); Democide: Nazi Genocide and Mass Murder. (1992); Death by Government. (1994); and, Statistics of Democide. (1997)