Find me a hitter that consistently, year in year out, does drastically better or worse with RISP then he does in any "normal" situation. Its not a skill anymore then hitting for average is a skill. If Morneau is truly a 300 hitter then over his career he will more then likely hit around 300 with RISP. So don't worry about it.
"If you look long enough for an argument against reason, you will find it" ~Moneyball
There is a very fine line between "hobby" and "mental illness