Really?

Not that it's in any way correct to excuse bad behavior by pointing to the same, but I find this statement highly suspect.

If, in point of fact, someone at an Obama rally had called McCain a terrorist, why have we not hear of such?

There are plenty of pundits and commentators on the Right that wait with baited-breath for even the most minor of verbal-slip or random act by a supporter for this to be accurate.

Sean Hannity would devote an entire show to it if it had happened.

I know I like to stay clear of the "what if" situations, but anyone with even a moderately functioning brain-stem can see that McCain is simply trying to cover for his supporters by redirecting attention.