“There can be no examination of judges other than Impeachment proceeding”
Impeachment proceedings imply that impeachable offenses have been uncovered.
“Separation of powers”
Balance of power. The other two branches are supposed to keep an eye on the Judicial Branch. None of the three branches is empowered to police itself exclusively.
The only way of removing a Congressman is by his House. Neither of the other branches can do it.