That is a simple fact.
Did Romney have something to do with that decline? Who knows. But it is still a fact – crime went down.
It is like the fact that Bush was warned about OBL’s plans to attack America. Easy enough to check.
So why are Mitt Romney and Rudy Guliani fighting about it?
They are because Republicans have bought into this notion that there are no objective (provable) truths. Everything is open to debate. Everything can be spun. Ergo; there is no reality beyond the reality that exists in ones own head. This is a pernicious philosophy that is hurting America and it needs to be rejected everywhere is pops up.
A fact is a fact. Some help your case and some hurt you case – but the ones that hurt your case are still facts.