Can I sue an employer for discrimination?

Recently I reported a co worker for harassing me. He was fired and now all of a sudden im not making production quota. The managers treat me as if I was in the wrong for reporting the incident. I continue to do the same thing I have been doing to make quota. I watch other employees not work at all and still exceed quota. They have been there a lot longer than I have, and the manager treats them as if they are buddies instead of employees. They talk most of the day while im continuously working to make quota. At the end of the week I check my quota and im under, ever since the employee got fired. But his buddies all make above rate, while they talk all day. Other employees see this as well and say its not right but are afraid to speak up, in fear of being targeted by the same manager. The manager admitted to me that he boosts the rate if we are close to making quota, this has led me to believe that since his buddy got fired he can also decrease it.