The concern at the time was the arming of the state Militia. Since rights are protected for individuals, they couldn't say "the right of the Militia to keep and bear arms ...". Also, it wasn't their intent to have the second amendment protect the right to keep and bear arms for all persons or even all citizens.
So, in 1789, they protected the right for "the people" -- white male citizens only.
Please allow me to go here:
Who makes up the body of the State? I believe the people do. You can not say that it wasn't their intent to have the Second Amendment protect the right to keep and bear arms for all person or even all citizens, because the people are the State. We are the ones who will make up the State militia too. We have the right to protect our country against threats foreign and domestic. This is what the Second Amendment protects. Again, if they didn't want the people to have the right to keep and bear arms, they would have said you have to be part of the militia to have a weapon. They would have put out a mandate to turn your weapon in if you are not part of the militia or face stiff penalty, if caught with a weapon. But they did not do this because they knew that push comes to shove, people will join the militia and they will need a weapon and this is how the militia will be armed. Hence, the people's (individual's) right to keep and bear arms shall not be infringed.