Why do you think people feel so strongly about slavery

When people have been enslaved for many generations, and there are many people in the world who've had that experience, and are still having that experience, it's very traumatic.  It does a lot of psychological damage that can take many generations to reverse, and if that process is botched it can just linger on indefinitely.  Naturally, people have very strong feelings about something that influences their lives so intimately and negatively.

For example, a form of slavery, feudalism, was rampant throughout Europe.  People who'd been entrapped in it for centuries fled to America.  There they found a civilization where the former 'nobles' (slave masters) in the Old World considered them equal human beings!  And all they had to do to achieve that equality was point their fingers at Black Americans and call them the inferiors (slaves).

Unfortunately, this was not a legitimate form of emancipation and it did not heal any of their problems.  It's all been festering now for two, three hundred years and they haven't made any progress at all on what ails them.  The only hope they've found has been the progress Black people have made in emancipating themselves in a legitimate way.  Many whites have found some degree of recovery.  You'll find them identifying themselves as 'anti-racist. ' That's generally coincidental with people into 'personal growth.'  

Their less fortunate, disadvantaged white brethren who still ascribe to the delusional form of so-called equality and freedom are rarely ever the achievers of any kind of personal growth.  So, you see, the post traumatic stress disorders from their unfortunate experience in Europe have remained intact to this very day, and impact their lives strongly, hence their strong feelings about slavery, that, if they're still in a state of denial about these oppression issues, have become quite twisted.

the answer is a) to be able to obey them.