Whenever I'm on a team that is like that, I make the most of it (it's almost always because I joined the team solely because my buddies put a team together, and they might just not have played at a very high level or something like that), but fill the water bottles with beer and have a laugh...it's a beer league after all!
If putting up points is important and you really do care about winning/losing, then just stop passing them the puck as often and only use them as a get out of jail card; and just skate the puck out. Also if you cause turnovers in the neutral zone, standing up at the red line instead (much easier to type than to actually do!), then you lead the transition back up the ice and are the primary puck carrier.
No real nice way to tell someone they suck in a beer league, because odds are they know they do, but are playing for fun. I would think everyone would know that the play dies on their stick more often than not.