The only real issue for whether Fifty Cent should be allowed into the country is his criminal record. The usual test for that is if there is a risk that he will re-offend while in Canada. I don't have a lot of fear that Fifty Cent is going to get into a gun batle while he's here.
The other factor that should be considered, because those that would keep Fifty Cent out have made it an issue, is that there was a shooting at the last concert that he had in Canada. Since there's likely to be a rather violent demonstration if the concert is cancelled, it's likely better to let the show go on.
Besides, somebody got knifed at a Waylon Jennings concert I was at once. I never saw it and didn't know about it until I saw the news the next day, but it still happened. I doubt Jennings ever heard about it. Waylon was known abuser of cocaine, a sometimes violent drunk, had a reputation for being a little hard on hotel rooms, was a proponent of firearms, and his music was disliked by a lot of people. He came back to Canada several times for major tours after the knifing incident.
Let Fifty Cent come and do whatever it is he does.