professor pushing me to get result when nothing is right!
The case as I understand it is:

(1) You are taking a course and the assessment is based on      producing a publishable paper based on a pre-assigned topic. 

(2) The topic assigned to you is not your research interest and appears to be broken, whereas other classmates have been assigned more appropriate topics.

(3) You feel that you are forcibly being roped in to fix someone else's problem.

Point (1) means the professor has the right to set assessments as per his judgement. There's nothing you can challenge here. No, you can't refuse to work on it (unless you forego the grade).

Point (2) is unfortunate, but it's inevitable that some inequality will exist between students. You can voice your objections, as you have already, but it's entirely the prerogative of the professor to act upon them. I would suggest making a calm and composed case mentioning only the perceived differences in difficulty of your project vs other projects. Don't talk about what flaws the project has. It might be a good opportunity for you to try correcting them. Maybe you were assigned this because you have a particular aptitude. Don't fight it before trying everything at your disposal. 

Point (3) is a serious charge amounting to ethical misconduct. If true, this should be reported and escalated to the relevant authority. However, keep in mind that this is your interpretation only, possibly subject to bias. If you choose to act upon this, do think long and hard first, being as objective as possible.