I would say that not loving one's neighbor does not demonstrate your faith. You seem to forget that James' challenge in 2:18 was how one can demonstrate their faith without works.Hi freegrace, here is another example of the confusion you have over this issue, precisely because of your attempts to isolate belief, faith, love and obedience from one another. You can't do it without becoming irrational in your argument. For example, you said:
"Loving one's neighbor DOES demonstrate our faith."
The opposite is true as well. Refusing to show love to one's neighbor demonstrates a lack of faith.
WHAT?? No, it shows disobedience on the part of one of God's children, and that child will be subject to God's discipline per Heb 12.If we are saved by faith (which you've made abundantly clear that we are), then refusing to show love to our neighbor will result in no faith and no salvation.
Your last sentence is a non sequitor. They are not causally linked, and there are no verses that make that statement.Jesus said, "If you love me, you will obey me" and "those who obey me show that they love me" (John 14:21 , John 14:23). Loving your neighbor is a command. Doing so demonstrates faith in Jesus, but also love for Jesus. There is a clear connection between faith, love and obedience. You can't have one without the others. They are all expressions of one another. One will always lead to the other.
If they were causally linked, there would be NO NEED for the command to love one another. The existence of the command proves that they aren't causally linked.