“As they plot their crimes, they say, ‘We have devised the perfect plan’.” All criminals or evil people think they have devised a plan so skillfully they will never get caught. David’s complaint in verse 1 was not about God but about evil people.
Notice that David’s comments are primarily figurative. The arrows he is referring to are speech, a common sin with all humans. God said, “You must not testify falsely against your neighbor”. Exodus 20:16. Yet, many people think they have the right to spread rumors without knowing the whole story or by simply making things up for whatever purpose.
I was taught many years ago that in Romans 1 Paul lists a progression of sins; the further you read his list the worse the sin. Now Paul deals with homosexuality in verses 24-27, but he deals with gossip in verse 29. So which sin does God think is worse?