Most of the human being has a tendency to rule over others. Sometimes this characteristic is treated as a good one, but in other cases it makes no sense. Because the later group of people do not have any novel instinct in them. They just want to do this for their own purpose. Besides these, some people out there we never think of doing well to other. They just possess a mind set that, they have to harm others and take benefit of them. Usually in these scenarios the victims are good individuals who are apprised for their novel deeds. These people are normally of simple mentality; even if some one hurts them they do not protest it. They just continue with their usual simple life. That is where the evils are evoked to harm them. So it will not be a viable option to stay as a Mr. nice guy anymore.
If someone wants to take advantage of your good side, then protest it. Try to make them realize that, what they are doing is not a good ting. Try to have command over their cognitive process. Be confident and show that you have the gut to point out their mistake. Make them acknowledge their mistake. Go with rational process. Keep trying to pursue them.
If it does not work, then protest in their way. Show them how it feels when they hurt someone. Introduce them with the reality. This option does not necessarily mean you have to be as evil as them. Just give them a nudge and make them understand how evil they are. You have focus on creating the sense of compassion in them, that is what they lack and that is what you will be aiming for. Make a balance of Mr. nice and aggressive within you.
Here are the two most suitable choices: