Biden’s gaffes are due to his speech impediment. Forensic psychiatrist Bandy X. Lee, who edited a book that detailed Trump’s alleged mental decline, addressed the issue by stating that “Joe Biden does not nearly meet my threshold for signs of dangerous mental instability.” She added that she only “speak[s] up when there is a medical need of such great magnitude as to risk the survival of the human species. This is definitively Donald Trump, not Biden.”
I still use the substitution avoidance method at times myself to avoid blocks, as Biden does. People who stutter have to remember how to talk as well as what to say. It can get exhausting, especially in a tough campaign.
Sometimes I ramble off the topic, searching for the patterns that will return confidence and a semblance of fluency. At those points, it’s not so much the words I’m saying, as saying something, that helps me find a path back.
Bottom line is stop attacking Biden over his speaking problem. Focus on issues, but you sound like Trump supporters when you attack him over this.