Article 3, Section 2, Clause 3: The Trial of all Crimes, except in Cases of Impeachment, shall be by Jury; and such Trial shall be held in the State where the said Crimes shall have been committed; but when not committed within any State, the Trial shall be at such Place or Places as the Congress may by Law have directed.
It would appear that you have a constitutional right to a JURY trial as long as your crime is committed within one of the states of the Union.
But fair? Please. A jury trial is often a dirty fight. We all hope for fair. But you know as well as I that what you get is a mixed bag of fair and unfair. We all know there have been instances of someone going to jail or the chair because of police corruption, judge corruption, attorney corruption, to whatever degree they are corrupted or have it in for the victim. Once in a while you encounter some honest people in the legal system and you get a break. But it is a mix. No fair anything is a constitutional right; you wouldn't have fairness if it were.
What you do get from the Constitution is a chance. A chance to fight fairly or dirty, it is your choice, but in that trial room you have your chance to prevail. And that is better than other countries that will throw you in the dungeon just for opening your mouth and forget about you.
Logical deductions are fine, as long as you start with valid premises, but your argument begins by referring directly to a specific clause which by your own admission is not there. And that is an invalid premise that will yield an invalid conclusion, which in this case is, "which forbids government endorsement of religion in any way." How do you get that conclusion with fidelity when your premise, the clause, is non existent? If your conclusion is true, you should go find a valid premise and show it to us. Don't make it up! What you are doing is called manufacturing evidence, and that is not well receieved by people who can see what you are doing.
And you hurt your own case because your earn the distrust of people by your own transparent efforts to offer fraudulent, deceptive and defective arguments. Then it no longer matters that your conclusions may be right. Your flawed logic will trash the whole thing.
That said, I agree with your last paragraph. Making people pledge allegiance is something I expect under an unfree government. It smacks of indoctrination. As if to be an antidote for popular contempt bred by injustice suffered by the people. Free people do not need to be indoctrinated. And if the government is just, and the people are free, their allegiance will exist naturally and be expressed in their daily behavior as well as their response to protect their land against threats.