According to senator bruce, what things should determine a person's political party affiliation?

The sober American judgment must obtain in the South as elsewhere in the Republic, that the only distinction upon which parties can be safely organized and in harmony with our institutions are differences of opinion relative to principles and policy of government, and that differences of religion nationality, or race can neither with safety nor propriety be permitted for a moment to enter into the party contests of the day. 

1. the spread of reform movements aimed at perfecting american society