Well you have to consider that Lars, circa 2012, is talkin' not Lars circa 1981.
Metallica is at a point FAR different than they were at in 1981.
At the time Ron McGovney fit the bill....til they saw Cliff. All of a sudden wonderboy Ron, James' good friend, has gotta go! But they cut him with ♪NO REMORSE! NO REGRET♪ etc.
In 1981 the guys didn't see themselves someday playing poppy stuff that worked for some single mom out in Nebraska, or grandma. They were out to destroy. Thus Cliff fit the bill.
Metallica, NOW, is a different creature altogether. Just the same, Cliff was a BIG R.E.M fan so who's to say, if he tried out now, he wouldn't make the cut??
Personally I don't like Lars, the public figure. I don't know him *personally*. For all I know he might REALLY be a dick, or just be a guy who has a knack for saying dick-ish stuff. Mustaine's bio makes Lars out to be a 101% prick. I hear from drummers that his playing is nothing to write home about. Maybe so, I wouldn't know since I'm not a drummer. At the end of the day, he's helping to run a multimillion corporation called "Metallica". Sad truth, kids, is that you don't run multimillion dollar corporations being all soft & fuzzy. Look at Gene Simmons of KISS. Major prick, but he never has to worry about if he'll make enough next payday like you & me.