The idols are not good (Ps 16:4-16:4)

“Those who choose another god

Multiply their sorrows.

Their drink offerings of blood,

I will not pour out.

I will not take their names

Upon my lips.”

Those who do not choose Yahweh will multiply their sorrows. The psalmist will not partake in their blood offerings. He will not let their names pass his lips. These idol gods are the opposite of Yahweh. They are not good. Thus they are evil.