In "Civil Disobedience," why does Thoreau think that a small handful of individuals can get away with perverting the government?If possible, please...

At the start of this essay, Thoreau argues that the war
with Mexico proves that the government of the US can be perverted by a relatively few
people.  To me, he is saying that the war is made possible by the fact that most of the
people of Massachusetts (and presumably other states as well) just do not care enough. 
I believe that it was Edmund Burke who said that all that is required for evil to happen
is for good men to do nothing.  This is, I think, what Thoreau is
saying.

Thoreau says that most people in Massachusetts, at
least, do not like slavery.  But they do not really care enough to do anything about
it.  Instead, they just go about their daily lives and don't pay that much attention to
slavery.  As Thoreau says:

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There are thousands who are in opinion opposed
to slavery and to the war, who yet in effect do nothing to put an end to them; who,
esteeming themselves children of Washington and Franklin, sit down with their hands in
their pockets, and say that they know not what to do, and do
nothing...

To me, this is why
Thoreau thinks the few can win out.  The majority dont' care enough to stop the few and
so the few can pervert the government.