You are clearly not reading the passage that you posted:The question posed by the thread's title seems to be Giuliani's main "defense" of Trump.....
The first question as to whether a sitting president can or cannot be indicted is one that, eventually, the SCOTUS must resolve....
But much more important, is a sitting president cannot be indicted, all that means is that he or she is ABOVE the law....and not that he or she is innocent.
There is absolutely no doubt that a sitting President can be indicted.
Article 1, Section 3 paragraph 7 of the U.S. Constitution states:
"Judgment in Cases of impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law."
However Mueller cannot indict the President under current DOJ rules. Since the current rules disallow a Presidential indictment, the President could fire Mueller for violating those rules.
If that happened, the indictment would still stand. So effectively Mueller would be out of a job, but the President would be indicted.
Judgment in Cases of impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.
This statement says the exact opposite of what you claim - once convicted the president is removed from office. What this passage is covering is that Congress is not the judicial branch. They cannot, for instance, sentence Trump to jail time for a crime that they convict him of in office. Instead, they impeach him and on conviction they are removed from office and subject to all of the standard procedures that the Judicial Branch would normally go through to convict them again in a legal setting.
I believe this passage serves 2 primary purposes; to ensure that congress does not try and act like a court and actually sentence people and to remove any idea that an impeachment would remove the ability to convict in a court under double jeopardy.