Tiberius Claudius Drusus Nero Germanicus, Emperor of Rome after the murderous and assassinated Caligula, AD40 approx, had a stammer and was thought by the people. and even his family, to be a jibbering idiot.
In actual fact, like Abbott being a Rhodes scholar, he was one of the most astute, cultured, and politically clever Romans, cool and calm in a crisis, highly educated and a gifted historian, and ultra wise during his popular rule. And most of the time he had no stammer at all. The whole populace of Rome was stunned and amazed at his lion heart and his diplomatic skills.
You may find it funny if, as it seems, Abbott sometimes has a slight speech impediment or hesitation getting his words out at times of stress or pressure. Perhaps it is a mannerism in forming one's words before one speaks. It does not show any lack of strong intellect.
I think it's rude and in shockingly bad taste taste for you to be so ignorant in taking the "mickey" out of him and his way of speech. It's a sad reflection on how many people falsely assume things of others, and subsequently make fun of others regarding what could be a harmless minor impediment.
Disabled people generally have a lot to contend with. I have such a person in my family. They certainly don't need smarties and bullies making fun of them.
