I hope this post provides some additional ideas for discussion though some great points have already been made. I am going through a similar situation right now with a friend who has heard a lot about Christ for the last four years or so and is able to accept Jesus as a god but only as one among other gods. The comment I hear the most is, “It doesn’t matter what we follow as long as we love others”. It is true that the fruit of worship to the true God results in love for others but one question to contemplate on is, “Would God define love the same way as man does?”
When we are recipients of a kind act, when we feel an urge in us to stop suffering, whether Christian or not, we could be experiencing the vestiges of God’s image that continues to remain in man, the moral law written on our hearts. That is definitely to a degree a reflection of God’s love. Are we though as humans too quickly satisfied with this love we show? What if we could have been conduits of greater love that we have not yet experienced? Are we prematurely comparing the love possible without Christ and the love possible with Christ? How can we as men even define love with our limited perspective? If love is doing good, even well-intentioned love that is misinformed cant bring about good for another. We need true revelation to truly love. What if we could be more fruitful in our love to others being directed by the Spirit of God, as for example when Christian brethren warned Paul about his travels in Acts 21. We as humans tend to define love as alleviating all kinds of pain but a love that reveals our pride is often not seen as love. Yet, there are so many stories of Christian missionaries understanding God’s love when in extreme pain, a love only God can teach as he works on our pride. To discern love man may look at acts of social justice but God looks at the heart.
1 Corinthians 13:3-7 NKJV
And though I bestow all my goods to feed the poor, and though I give my body to be burned, a but have not love, it profits me nothing.  Love suffers long and is kind; love does not envy; love does not parade itself, is not puffed up;  does not behave rudely, does not seek its own, is not provoked, thinks no evil;  does not rejoice in iniquity, but rejoices in the truth;  bears all things, believes all things, hopes all things, endures all things.
In this definition, we also see that love rejoices in truth. I think we must not be fooled by abilities such as love, joy, peace, patience, kindness, goodness, gentleness, faithfulness and self-control if its purpose is not for objective truth based on reasonable evidence. With these abilities, we could probably manage without Christ in our earthly life, but if we have a soul that outlasts our body, we would want hope based on truth not just fruits in this life. So it may be important to ask, “What is the hope offered by these other faiths?”
Another thing to consider is that it’s easier to walk in what appears as the fruits of the Holy Spirit or love while ignoring doctrinal differences of faith as in new age. To walk in unity while facing the differences will quickly reveal the depth of love and the genuineness of the fruits! We have to be careful in our discernment of what we perceive as love.
Finally, I want to talk about the example of the Pharisees who thought they followed God’s law, yet couldn’t love His own Son. What value would our love bear if we chose to reject the love of God’s only Son, if the story of Jesus were to be true? In Matt 21:33-44, Jesus explains through the parable of the vine dressers how we can reject what God considers chief and valuable bringing ourselves under condemnation.
These are just some thoughts I am working through for my situation as I seek answers. I will stop here and hope they are helpful. It seems like you are having good conversations with your friend. May God continue to bless these conversations and bring your friend closer to truth!