John 13:34-35
A new commandment I give unto you, That ye love one another; as I have loved you, that ye also love one another. By this shall all men know that ye are my disciples, if ye have love one to another.
Real Christians will love those that even hurt them. Real Christians will love those that do them wrong. Real Christians have a love that goes past faults, failures, wrongdoings, etc. It is God's love because God is long-suffering and He died for us while we were yet - what? SINNERS! You can tell whether someone is a disciple of Christ by his love towards ALL.
I've always kept a watch on those who claim to be Christians but keep a list of wrongs. Those who will treat you differently if you didn't say everything "just right" to them or worship them like others. Those who snub you because they are so bitter against you for who knows what. Those people quite honestly aren't disciples of Christ - they don't have His Spirit! God IS love - there is no way around that.
So don't be downhearted when people treat you like that, just know that they are either not right with God or they are not even His. Pray for them. LOVE THEM ANYWAY! One thing I've always done is love those that have done me wrong, no matter how great the wrong - I still love them. Even those who maybe I made upset by something I said or did - they may not love me, but I love them.
I believe God sends us people our way that will hurt us or say things about us as a test to see if we will STILL love them. If you find you are coming across a lot of people like that or you are being "attacked" - realize that God allowed it and maybe, just maybe, he is waiting on you to respond correctly by loving them still.
I was reading various commentaries on these verses and I liked what Barnes had to say:
Christians will love their own denominations less than they love the spirit and temper of the Christian, wherever it may be found.
There are some that only view you as a Christian based upon what denomination you are but LOVE should be our measure of who is and who isn't a Christian. When you pick up on someone that has the Spirit of God, you won't care what church they go to - your Spirit bears witness. Denominations are a display of love as they help separate us and our differing beliefs on what the Bible says, so we won't always be striving about. No matter what church you go to, if you don't have love, then you don't know God!!