I'd be more willing to let is slide as a slip up if not for the surrounding context — both during the debate, and during the days following.
The whole premise of the question (https://www.youtube.com/watch?v=qIHhB1ZMV_o) was his criticism of Biden for not specifically calling out antifa and other left-wing extremist groups, and whether he'd be willing to "condemn white supremacists and militia groups" and "say that they need to stand down and not add to the violence".
Mistake or not, he didn't condemn the proud boys during the debate. If it was his intent to do so, when it became clear that large portions of the country misunderstood his remarks — including the proud boys themselves — he should have clearly communicated his intended message, instead of dodging questions about his remarks for 2 days. (See, e.g., https://www.whitehouse.gov/briefings-statements/remarks-pres...)
The whole premise of the question (https://www.youtube.com/watch?v=qIHhB1ZMV_o) was his criticism of Biden for not specifically calling out antifa and other left-wing extremist groups, and whether he'd be willing to "condemn white supremacists and militia groups" and "say that they need to stand down and not add to the violence".
Mistake or not, he didn't condemn the proud boys during the debate. If it was his intent to do so, when it became clear that large portions of the country misunderstood his remarks — including the proud boys themselves — he should have clearly communicated his intended message, instead of dodging questions about his remarks for 2 days. (See, e.g., https://www.whitehouse.gov/briefings-statements/remarks-pres...)