words of a pagan becomes the word of God

According to the Bible Solomon became a pagan at old age.

As Solomon grew old, his wives turned his heart after other gods, and his heart was not fully devoted to the LORD his God, as the heart of David his father had been. (1 king 11:4)

The Bible goes as far as saying anyone who trusts an idol worshiper becomes like them.

Those who make them will become like them, Everyone who trusts in them. (Psalm115:8)

But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people. (1 Corinthians 5:11)

Here’s the problem, if putting trust or associating with an idol worshiper is wrong. Why would you accept the writings of such individual and claim it to be the word God?

Solomon supposed to have written 2 books which are part of the Bible. The same Solomon whom the Bible says became a pagan, idol worshipper! So now Christians have to admit they have 2 books in their cannon, “the Songs of Solomon and Proverbs”, both written by Solomon who was a pagan?

If Christians have no problem preaching the words of a pagan, then why cant they also preach the words of Satan?