Why get offended when you know you're right?

[Esquilax]

The same could be said about some atheists...

Nobody's saying it couldn't. Nor does the fact that some atheists have issues admitting wrongdoing invalidate the fact that some religious folks do too.

It's a very human thing to do, really; we rarely get challenged this directly about beliefs that inform so much of ourselves, so it's almost an automatic reaction to continue assuming that you're right, and to leap to their defense, with offense. Those of us who manage to keep that impulse in check and actually examine the evidence and allow that to inform our views, end up at least agnostic.