Jesus was fiercely hated by the religious leaders of the day because He publically and directly confronted them on their hypocrisy. They had distorted and added to the message of God so much that it had become a heavy burden upon those who would try to live it (Matthew 23).
The Gospel of Jesus Christ is SIMPLE, yet radical, in that it challenges us to the very core of our being. It is the antithesis of worldly wisdom and systems. Rather than being 'me-oriented,' it is 'others-oriented.' It is offensive to all those who believe that life and eternity should be merit-based. Rather, it informs us that the way is narrow -- we cannot enter the Kingdom of Heaven with our "stuff," be it our sin, be it our accomplishments (Matthew 7:13-14).
Most importantly, it constantly brings us to a place of recognizing our spiritual poverty -- we simply cannot do it on our own, but need God. He has freely given us His love, His grace, His mercy, His kindness, His forgiveness, and His compassion. We cannot earn it, work for it, strive for it -- it is a gift (Ephesians 2:8-9).
Yet, the ONLY condition to receiving these things is how we walk in relationship to others, and this is an area where the Christians you reference tend to lack. Jesus said (in relation to love, forgiveness, mercy, etc.), "Freely you have received, freely give (Matthew 10:8)." He illustrated time and again that those who refuse to forgive others as they have been forgiven will not be forgiven (Matthew 6:15; 18:21-35).
What is the Gospel? It simply means "Good News." What is this Good News? It is that, through Jesus Christ, God has made us right with Him (Romans 1:16-17).
It is written that everyone who calls on the name of the Lord will be saved (Acts 2:21).
“And that message is the very message about faith that we preach: If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For it is by believing in your heart that you are made right with God, and it is by confessing with your mouth that you are saved. As the Scriptures tell us, ‘Anyone who trusts in him will never be disgraced (Romans 10:8b-11).’”
Anything else complicates and compromises the beautiful simplicity of the Gospel.
Love in Christ,