Why did the constitution allow slavery to continue if "all men were created equal"?

Most white men thought they where better than people of color and treated them as garbage  

Viceroyalties were instiutions created by the Spanish monarchy to incorporate the colonized lands in America in the administration engines of the Empire. A viceroyalty was ruled by viceroy, a direct subordinates of the King, and was considered a province within the Empire and not a colony anymore.

The two viceroyalties existing in America prior to 1717 were:

Viceroyalty of New Spain. It contained the current territory of Mexico, together with Southwestern states from the current US. It was the first one created by the Spanish in America in 1535. Viceroyalty of Peru, created in 1542, which contained almost the whole territory ruled by the Spanish in South America.