maybe it is debatable about whether the teaching in the quran is to kill
only the non-believers that converted and then turned away, or the nonbeliever that refuses to believe and thus is seen as a threat, but the hadith spells it out clearly that it is for all that leave the faith.
again from quran:
They wish that you reject faith, as they have rejected (faith), and thus that you all become equal (like one another). So take not Auliya (protectors or friends) from them, till they emigrate in the Way of Allah (to Muhammad SAW). But if they turn back (from Islam), take (hold) of them and kill them wherever you find them, and take neither Auliya (protectors or friends) nor helpers from them.
( سورة النساء , An-Nisa, Chapter #4, Verse #89)*
again from ahadith:
*Sahih Bukhari, Volume 9, Book 84, Number 58:
"…Behold: There was a fettered man beside Abu Muisa. Mu’adh asked, “Who is this (man)?” Abu Muisa said, “He was a Jew and became a Muslim and then reverted back to Judaism.” Then Abu Muisa requested Mu’adh to sit down but Mu’adh said, “I will not sit down till he has been killed. This is the judgment of Allah and His Apostle (for such cases) and repeated it thrice. Then Abu Musa ordered that the man be killed, and he was killed…”
Sahih Muslim, Book 016, Number 4152:
“'Abdullah (b. Mas’ud) reported Allah’s Messenger (may peace be upon him) as saying: It is not permissible to take the life of a Muslim who bears testimony (to the fact that there is no god but Allah, and I am the Messenger of Allah, but in one of the three cases: the married adulterer, a life for life, and the deserter of his Din (Islam), abandoning the community.”
*
if islam had there own catechism that clearly explained the meaning and declared officially that they only meant to kill them spiritually

it would be one thing, but the danger of the quran is that the teachings are supposedly eternal and meant for the inmams to interpret. not that it’s Scripture, but another fine case against the chaos of sola Scriptura!
i admire the small minority of muslims that have somehow wiggled around the violent teachings, but come on, you have to admit the “extremists” can build a good case of why they do what they do based on these writings.