He's just bitter cause they wrote him off the show.
But it was clearly the right time to kill him off.
The whole season built up to it.
Stringer thought he could rise from just a thug on the street to a corrupt businessman. But the actual corrupt businessmen knew how to con him and then his ways on the street caught up with him.
There was no way he was making it to season 4.
Granite he was a good bad guy. Way better than Marlo. But he had to go.