I think condition 51 is a good thing, yet it's really flawed at the same time. It has it's pro's and cons and I don't think they should remove it, but modify it instead to make it less flawed. I agree that people who are in a abusive relationship (especially mental abusive relationship, since it can be harder to prove) are pretty much screwed by condition 51. But condition 51 helps those sponsors who just get used by their partner, and in a lot of cases if the relationship doesn't work out, why should you stay in Canada then? But at the same time it's unfair for the people who are in a abusive relationship (or people from certain cultures getting in trouble when they go back, unless he/she used the sponsor) to be screwed over by a condition 51.
Long story short, I think they should keep condition 51, but modify it more so it also protects the applicant.