A small point: Congress, the House, and the Senate, are not courts or form a court. The Members of Congress are not necessarily lawyers. Strictly and literally, then, lawyers are not needed for the arguments when Congress does an impeachment. Again, Congress is just not a court of law. So, if an impeached person wants help in their defense, they don't have to hire lawyers.

My point: If a person helping with a defense is not a lawyer, then the legal profession can't disbar them.