If their deaths are intentional why would it help to ask them to stop? I think you know they were having a bad game and that their deathswere not intentional and you just saying "stop dying" is not helpful.
In fact, anyone who can just "stop dying" at will but still be doing anything outside of the base should probably be challenger, since most deaths are not intentional.
The short answer is to stop saying that stupid shit any time someone is having a tough game. The more they try to hide from action the more their level will fall behind and the more they will die anyway. Stop calling a bad game intentional feeding. Stop saying you are going to report people for having a bad game. YOU are the problem. You didn't get banned for doing this shit just once either.