Although these historical figures made grievous mistakes, they also contributed to America in positive ways. Columbus championed the exploration that eventually led to America's first European settlements. After becoming an orphan at fourteen, Jackson became the most powerful figure in the United States. During his presidency, he advocated zealously for democracy and the common man. 
Both of these people made poor decisions, but their stories are complex and cannot be dismissed as simply negative. We should preserve these statues as celebrations of their contributions to America because even imperfect historical figures deserve recognition for their good work.