It's disappointing to hear Marty speak this way. I have no problem with him saying things like "Dunn needs to work on cutting back on strikeouts," or "it would be good to see him shorten his swing at times," but to say he's ready to give up on a player is a bit over the line to me.
I completely agree that it's hard to be Babe Ruth and Tony Gwynn at the same time. The trend seems to be that if you hit for average, you stand a good chance of cutting back on your power. Honestly, I could stand giving up 10 HR a year if it meant increasing his RBI count by 20 and improving his OBP.