Marty was trying to push Rohan backwards legally over the goal line by backing into him, and you actually see Rohan lift Marty both feet off the ground and swing him behind him.
No one seems to be blaming Marty for being "out wrestled", more saying he needed more support than being allowed to be caught one out, but no one seems to want to give credit to Marty for covering him legally only to be picked up and slung behind illegally.
Any player could probably pick up any other player from behind, to wrestle back you need to have a hold of the other player. And, as everyone says, if Marty did it to him there would at least be an outcry of cheating and a free kick if the umpire saw it.
See the Marty thread if you want to see this.