He vetoed it for various reasons. For starters, he believed that it was a thing up to individual states and that it infringed on the states right to choose. Another reason was that he believed that such beneficial extension would not make people equal, but rather it would be racist towards the white people. His main argument, however, was that the bill would have a certain group gain rights that they are not entitled to, while a large part of the states does not even have representation in the congress, and that the congress needs to be enlarged first.
