He's been calling Trump a threat for years and then when bullets fly it's wait it a minute I take it back. You can't play up your opponent as the biggest threat to your country and then ask for calmness when shyt goes down. Its the same for the GOP and acting all tough and when shyt happens they become the biggest victims known to man.
He's not taking anything back. This country has been tense as fukk for the last 8 years because of Trump and his allies in the Republican party. There has been an increase in radicalized people and that comes from political rhetoric, (that is really just hate speech and incitement of violence from Republicans), conspiracy theories, misinformation, isolation, etc. Family members and friends who have different political viewpoints now argue over politics so strong that they don't even talk to each other anymore because of Trump. Or if they do, it ends in an argument and hurt feelings. Biden directly addressed this when he said "We are not enemies, we are Americans"
You tripping right now man. Stop acting like one of these weird leftists on twitter. Calling for unity does not make the President weak.