Why do Calvinists react differently here?

Uh, remember, it was the Calvinists who always made hardening in Romans 9 (and "blinding" elsewhere) synomymous with "DEAD in trespasses and in SIN" to justify the notion of God offering salvation to only some and passing over the rest. Rom.9 was thrown up every time someone had some question on this, and this is what led to all the focus on hardening.