I think I address your point with...

"You seem to focus on one statement by Biden and it would be wrong to suggest that one statement was likely behind the shooter's decision to assassinate Trump"

So, Biden is not to blame, nor is he blameless. Those that engage in fearmongering all share in the blame when people react and respond to the fearmongering.

https://www.msn.com/en-us/news/other/biden-has-staked-his-campaign-on-painting-trump-as-a-threat-to-democracy-that-could-change-after-saturday-s-shooting/ar-BB1q1Iqr?ocid=BingNewsSerp