Basically: I committed a crime while trying to stay in office illegally, but you can’t hold me to account because I’m running for office.
Pretty much “I’m a big-deal Republican, so you can’t apply the normal rules to me, even though others have run for President from jail”
Trump has literally argued in court that the President can do anything up to and including the assassination of a political rival with no repercussions other than impeachment. By extension, that includes the arrest and assassination of members of Congress and the courts who would oversee his impeachment and/or prosecution. They argued that this is a protected right of the office of the president in the constitution, in front of a judge.
To point out that if the same logic were to be applied by Biden to solve the Trump problem is simply showing the absurdity of the argument. You can unclutch those pearls.