Inform, Educate and Motivate!
Congress' separate retirement and medical insurance systems set them apart (and rather above) the people at large.
That makes this practice a defacto "Title of Nobility" - it places them outside (and above) the law that applies to the people at large - We the People.
Titles of Nobility are rendered unconstitutional in Article I Section 9:
No Title of Nobility shall be granted by the United States:
Thomas Paine wrote Common Sense, the book that more than any other led to The Declaration of Independence. Later he moved to France where he wrote The Rights of Man and the Citizen. Strictly speaking, this document is not a part of the Constitution. But given its author's close ties to the revolution, the thoughts in it deserve some weight.
The law must be the same for everyone, whether it protects or punishes.
Definitely, the separate rules for Congress regarding retirement and medical care violate Paine's reasoning.