He was ostensibly in Kenosha as part of a militia that opposed Black Lives Matter. Literally the only reason to oppose that movement is white supremacism.
He's been seen hanging out with Proud Boys since; they're a violent white supremacist terror group.
The judge had to adjust the terms of his bail a couple weeks ago to state he was no longer allowed to hang out with white supremacists, because Rittenhouse was doing so flagrantly.
He's flashed White Power symbols himself, personally.
I don't need to see his Klan hood literally on his head to figure this shit out.
And no; recognizing that this shithead is a white supremacist doesn't reduce the merit of the evidence arrayed against him or indicate that it is somehow weak. I have literally no idea where you're getting that concept from.