According to John Winthrop, what is the source of the trouble between Magistrates and the people?

In "A Model of Christian Charity," Winthrop understands that the new society settling in Massachusetts will consist of the rich and the poor. It is God's plan, he says, that some will have many material resources and some not enough. Some, too, are made to rule and some to obey. God has created the world this way in order to inspire his believers to practice perfect love and charity to one another, and so be more perfectly knit together as one body in Christ.
Winthrop says that the source of trouble between magistrates and people is a sense that the two groups that are different from one another. As he puts it, people have a "will" or tendency to be attracted to those they perceive as like them. He states that

for as of things which are turned with disaffection to each other, the ground of it is from a dissimilitude or arising from the contrary or different nature of the things themselves ...

In other words, if people don't like each other, it is because they believe their natures are different.
However, says Winthrop, people who love each other feel that are alike. They have "some resemblance" to one another:

for the ground of love is an apprehension of some resemblance in the things loved to that which affects it

Therefore, the basis of the new society must be the deep and visible love members of the community show to one another. Winthrop calls for "fervent love amongst" his people. Those who have wealth must give generously to those who don't, and those who receive must do so in loving obedience. Everybody must, in a loving, just, and merciful way, understand their place in the social order, for:

no body [of people] can be perfect which wants its proper ligament [order].

Winthrop warns that if the people in a community such as this, chosen specifically by God to be a light for other nations, a city on a hill, should fail to show God's deep love to one another, regardless of their social position:

the Lord will surely break out in wrath against us, and be revenged of such a people, and make us know the price of the breach of such a covenant.

Love pouring out is the answer to social problems; lack of love is the cause of trouble.