It has been objected also against a bill of rights, that, by enumerating particular exceptions to the grant of power, it would disparage those rights which were not placed in that enumeration; and it might follow by implication, that those rights which
were not singled out, were intended to be assigned into the hands of the General Government, and were consequently
insecure. This is one of the most plausible arguments I have ever heard against the admission of a bill of rights into this
system; but, I conceive, that it may be guarded against.
- James Madison, 1789
According to Madison, why did some people oppose the addition of a bill of rights to the Constitution?

Limited the rights of Americans

Explanation:

The Bill of Rights was the compromise that eventually got the Anti-Federalists to agree to ratify the United States Constitution because they had been worried about the Federal Government being too powerful.

We can see from here however, that there was opposition to the Bill of Rights.

The opponents argued that if particular rights were outlined specifically, the rights that were not outlined in like manner may be abused by the government which in effect would lead to the Bill of Rights limiting the rights of the very people it is meant to empower.

James Madison however, believed that the risk of this could be mitigated.

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