“Kill the unbelievers”, “death to the apostate”, “slay the blasphemer” …
Such ringing phrases are evidence of a faked belief in ‘God’ – or ‘Allah’, or whatever other name is conferred on ‘him’.
Because there are only two possibilities here for believers: either God has given us free will or he hasn’t.
If God has given us free will, then killing someone for using that divine gift is bizarre … like cutting down an apple tree to punish it for producing apples.
Or if God has not given us free will – if we are all just following pre-destined paths decreed by God – then it’s equally bizarre to kill someone for doing something they were designed and intended to do … and in fact had no choice but to do.
And if God exists, then again there are only two possibilities. Either ‘he’ will judge us individually after death, or he won’t.
If God will judge us, then why should any believer presume to substitute their judgement (and their decreed punishment) – and pre-empt God’s – by deciding that such and such a person is a ‘blasphemer’ and should be murdered/executed? 
After all, isn’t God supposed to be all-knowing and all powerful? Yet so many ‘believers’ are keen to substitute their ‘knowing’ and their ‘power’ for his.
No, underneath it all such fanatics are simply faking it … faking a genuine belief in God and following the local herd in trying to use loud breast-beating as disguise for their spiritual ignorance and confusion, disguise for their shallowness or lack of true belief.
“Look at me – look here – I’m willing to kill and condemn to death for God. See how devoted to him I am!” To quote Shakespeare, these are tales “told by an idiot, full of sound and fury, signifying nothing”.
Because, as ever, empty vessels make the most sound.
 Or if God does not exist, then the howling calls for god-sanctioned punishment become even more pointless.