Roswell, it would be a good argument today, where there are standards for capitalization
It doesn't rest only on capitalization , its the logical word usage based on accepted word usage to be found in our dictionaries.
The People in the collective sense is a Marxist Communist ideal of the People as an entity. In Anthropology and historical terms "A People" denotes a unique collective sense.
If the Constitution meant the collective sense it would read "The right of A People to keep and bear arms can not be infringed". Alternatively "The right of our People" if seperating the US Citizenry from other Peoples as a Unique collective People.
Its obvious from the word usage that People was meant in the plural as an indeterminant number of individual persons.
Thus
1plural : human beings making up a group or assembly or linked by a common interest
2plural : human beings, persons —often used in compounds instead of persons<salespeople> —often used attributively <people skills>
3plural : the members of a family or kinship
Rather than
4plural : the mass of a community as distinguished from a special class <disputes between the people and the nobles> —often used by Communists to distinguish Communists from other people
5plural peoples : a body of persons that are united by a common culture, tradition, or sense of kinship, that typically have common language, institutions, and beliefs, and that often constitute a politically organized group
In this last definition
7: the body of enfranchised citizens of a state
It remains a plural of Citizens, citizens being a number of Individuals, as opposed to the homogenous mass of the Communist Peoples.
Enfranchised
1: to set free (as from slavery)
2: to endow with a franchise: as a: to admit to the privileges of a citizen and especially to the right of suffrage b: to admit (a municipality) to political privileges or rights
Citizens are enfrancised on the individual level in a democracy just as your rights are yours to use or lose according to your own actions.
If you commit a felony you lose some of your rights as a citizen, but the rights of your fellow citizens remain intact.
In a Democracy rights are individual rights to be used or abused on an individual basis. The state exists to serve you rather than vice versa.
Any service you perform for your fellow citizens, beyond your legal obligations as a unique individual member of society, is voluntary.
Obligations are also individual according to your circumstances and abilities. If you fail to meet your legal responsibilities you'll be judged as an individual not as some gestalt Joe Public.