Garver made no attempt to maintain contact with the bag and it looks like he made an effort to 'pop up' and further interfere with the 2nd baseman (typically a pop up slide happens when you slide into the bag, which stops your momentum....in this case, Garver slides over the bag, so he shouldn't naturally pop up). He also doesn't slide right into 2nd as it's clear he's trying to slide into the 2nd baseman, while 'catching' the bag on the way by. I believe he went into 2nd with the intent of interfering with the 2nd baseman and support that ruling.
That said - this is definitely a borderline call and rules that have interpretation in them will also have that grey area where people argue both ways. No different then that right handed batter running to first on a bunt up the 1st base line and whether he's in the base path or not.
At the end of the day, this rule was the right call by MLB and I personally think it's improved the game. I can live with people bitching about a borderline call here or there (and really - how many calls have been questioned by this board over the past 2 years? Not many at all IMO).
Without that rule - there's a good chance that Bo doesn't even attempt that throw yesterday - and if he does, he might now be on the 60 day DL as it looked like a carbon copy of the Utley/Tejada play.