Oh ye it is..They worship false gods..
2 Corinthians 6:14 Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
The God of the Jews, the God of Islam, the God of the Philosophers and the God of Brahman Hindus, is the same as our God. Our paths diverge after that.
Granted, the Trinity has not been revealed to these other people, but we don't have a complete understanding of God's essence either.