This is speaking about worldviews and the working out of those worldviews. Certainly we can be friends with all kinds of people, and help anyone in need. But when it comes to spiritual endeavors and the seeking out of spiritual truth:
2 Cor 6:14
“Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness? What harmony is there between Christ and Belial? What does a believer have in common with an unbeliever? What agreement is there between the temple of God and idols? For we are the temple of the living God. As God has said: “I will live with them and walk among them, and I will be their God, and they will be my people.”
“Therefore come out from them
and be separate, says the Lord.
Touch no unclean thing,
and I will receive you.”
“I will be a Father to you,
and you will be my sons and daughters, says the Lord Almighty.”
oops sorry that was verses 14-18.