WHAT? You're going to have to provide the entire detailed argument for that one. That statement is really out there in left field.
A simple reading will do. Article I, Section 5, Clause 1: "Each House shall be the Judge of the Elections, Returns and Qualifications of its own Members, and a Majority of each shall constitute a Quorum to do Business; but a smaller number may adjourn from day to day, and may be authorized to compel the Attendance of absent Members, in such Manner, and under such Penalties as each House may provide." Congress decided, correctly IMHO, that those men who had just spent 4 years waging a bloody rebellion against the U.S. should not be the same ones to send Senators to Washington or sit in Congress. Congress has the right to decide on the qualifications of their own members.
Article III, Section 3, Clause 2: "The Congress shall have power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted." The Southern states, and their people, waged war against the United States. Their acts were, in all definitions of the word, treason. Congress ruled that one of the wages of treason was being barred from future positions of trust in the U.S. or representation in Congress until certain criteria was met.