The latest round of hearings has become an interesting exercise in set theory. We have the set of people who requested a pardon, the set of those who claim they did not request a pardon, and a third set of those that White House staff thought should request a pardon. When it's all sorted out, we will see the subsets defined by the intersections and unions of all the sets.
In the meantime, the main argument put forth by Trump supporters follows a central theme, which can be stated as. "the committee and all its staff are stupid."
It would be incredibly stupid to bring out a witness such as Hutchinson, without corroborating her testimony. A good part of Hutchinson's testimony was recitation of conversations with other people, notably the secret service agents. If the agents were so frank with her, what are the odds they didn't tell the same story to someone else? There will be other people who can testify, "Yeah, he told me the same thing." If the agents claim Trump did not try to grab the steering wheel and did not wrestle with his body guard, the next question is, why did you lie to so many people about it?
Side note: Secret Service training for handling the President in public is pretty specific. When a threat appears, such as a gun in the crowd, some agents are tasked with moving the President to safety and others are tasked with getting between the President and the gun. This is just for the sight of a gun. The Secret Service knew there were uncountable numbers of guns in the crowd. Taking the President into that situation could easily be interpreted as the set up for an assassination attempt. After the smoke clears, the first question would be, why did you let the President be exposed to so many gun?
There's really no way it could end without considerable casualties for civilians and agents alike.