سُبْحَانَ ٱللَّٰهِ
Holy Qur'an
Al-Qur'an
Kids Qur'an
This allegorical "question" - allegorical, because God is omniscient and has no need to "ask" - implies that many of "those who deny the truth" of God's messages delude themselves into believing that they are, nevertheless, worshipping spiritual forces, here comprised in the term angels".
Here we have the case of the worship of angels or supposed Powers of Allah, or supposed beneficent spirits that men turn to instead of worshipping the true God. In fact these are mere names to the false worshippers. It is not the Good that they worship but the Evil, which leads them astray.