By using various kinds of information, you can develop a good picture of your topic and write about it convincingly.
As the subject of social justice is very large, you will probably have more success researching it if you focus on a narrower topic within it. Below are a few ideas for focusing your research.
Civil Rights:
Law Enforcement & Criminal Justice:
Immigration:
Income Inequality:
Gender Inequality:
LGBT Rights:
Other Cultural, Ethnic, & Gender Minority Issues: