the slide was clearly and unambiguously against the rules. over the offseason they should make a point of telling baseball refs to call the rule as written.
it is a little unfair to suspend a guy for a play that, although against the rules, is seldom called. oh well, there are lots of things more unfair. if you don't want to get caught up in a sudden enforcement of an unenforced rule, don't go so far out of your way to flaunt your breaking of the rule.