I disagree
Morals are more likely corrupted one individual at a time. How easy the individual is to corrupt is determined by various factors.
Groups of individuals can be culturally corrupted by counter curtural values that denigrate education, respect for law and other time tested values.
Education becomes too white, manners become old fashioned and the law becomes a thing of contempt.
Who could deny that our racial problems would be less significant if we had been wise enough to welcome blacks into our culture sooner instead of forcing them to adopt the counter culture that plagues us now.