First, as has been pointed out, Biden was talking about moving the focus of the discourse back to Trump rather than to his leaving the race (reference below).
More importantly, you frequently use a rhetorical device know as "tu quoque." I don't know how to speak French or Latin so if I discuss this in conversation, I say "what-about-ism". It's a technique that's frequently used to avoid discussing weak positions.
I *wish* people, especially the lawyers here, would call you out on it because it hides 2 important facts:
1. you know your position is weak
2. you know your position is wrong
But people here let you slide. Biden apologized for his use of the word "bullseye." Did Trump apologize for any of his ridiculous claims? Trump's rhetoric was associated with increase hate speech and vandalism after his 2016 win. We're waiting for the repercussions of his stupid words just like we're waiting for his stupid policies.
I will call you out on your weak sauce rhetoric because it's boring. If you want to discuss things, man up and defend is dumb words.
According to Politico, Mr Biden had said on a private donor call: "I have one job, and that's to beat Donald Trump. I'm absolutely ceain I'm the best person to be able to do that. So, we're done talking about the debate. It’s time to put Trump in a bullseye."
https://www.bbc.com/news/articles/cd1rzde0n4do