Religious deception is how so many can do atrocities in the name of Christ and all the while think they are doing His will. It's how the Roman Catholic inquisitors could torture and murder so many of God's people and sincerely think they are doing God a service.
Thus it is with these people...
"They claim to know God, but by their actions they deny him. They are detestable, disobedient and unfit for doing anything good." Titus 1:16 (NIV)
We also aught to be patient with such, given their deception and bondage to the devil and his demonic teachings that they have turned aside from the truth to devote themselves to.
"The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons." 1 Timothy 4:1 (NIV)
"Those who oppose him he must gently instruct, in the hope that God will grant them repentance leading them to a knowledge of the truth, and that they will come to their senses and escape from the trap of the devil, who has taken them captive to do his will." 2 Timothy 2:26 (NIV)
Therefore...
"Rest in the Lord and wait patiently for Him. Do not fret because of him who prospers in his way, because of the man who carries out wicked schemes. Cease from anger and forsake wrath. Do not fret, it leads only to evildoing. For evildoers will be cut off, but those who wait for the Lord, they will inherit the land." Psalm 37:7-9 (NASB)