When something or someone is controversial, that means they are being debated based upon their ideas or actions. In the case of Martin Luther King Jr., he was controversial during his lifetime due to his actions against racial inequality. Instead of showing violence, he resorted to Gandhi’s methods of using non-violence by boycotting businesses. This was controversial because in most cases, people would resort to violence to get equality.
Now, King doesn’t do it that way. Also, King was controversial because he was trying to change the minds of the people into believing that everyone should be treated equally. This lasted for a long time which lengthened the controversy. Boycotting seemed like a useless way to get his point across, but it worked.