Assalaam Alaikum,
The evidences from the Sunnah are correct which JD has posted.
The murtadd is allowed 3 days and 2 nights to ask for forgiveness, afterwhich the hukm is as Rasool (saw) ordered, kill him.
Every rational/intellectual doctrine has a mechanism to protect/perserve itself and this is one of the ways...I don't see what the problem is!
We shouldn't be appologetic or shy away about such issues as we can prove the aqeedah to be correct by using enlightened thought and conclusive proofs.