> Before that fact causes you to lose sympathy for the case, note that almost every significant criminal case affirming constitutional rights involves a defendant who did something unsavory, if not reprehensible.

Not always. Often times prosecutors pick cases with bad fact patterns to be test cases when they want to attack a right. A recent example is Biden DoJ choosing to take US v Rahimi to SCOTUS in an attempt to wheel back the NYSRPA v Bruen decision.