This headline is needlessly disingenuous. Given the assassination attempt today, this headline is strictly inflammatory and out of context.
The context of the quote used, is not asking people to assassinate anyone, but to hyper focus the campaign to be effective and close ranks for the election... I.e. stop trying to get Biden to step down, focus on defeating trump.
In fact, this headline is so biased, it isn't even on the article itself.
Biden to Donors: 'We're Done Talking About the Debate'