I can only speak for myself, but keeping rules has not been my strong suit. In fact, my heart hurts when I start to become rulebound.
Fundamentalism says, "Keep the rules, and God will love you. Break the rules, God will get you!!" If that is the case, God has it in for me. I will never be able to please him by keeping the rules.
Liberalism says, "God loves you. There is nothing which separates you from God's love. not even breaking the rules!!"
For me, liberalism best describes the gospel as I have experienced it. It frees me to choose to live how God wants me to live. I acknowledge that what God has done for me, he is doing in all people at all times.
Fundamentalism is limited to keeping the rules. Just how many rules do you have to keep before God loves you? How good do I have to be?
When keeping the rules becomes our basis for living instead of our relationship with God, we will eventually turn on each other. If I don't keep the rules as well as you do, then I am less than you, and therefore, I am not as godly as you. There is no such thing as self-redemption. All our righteous (from Mother Teresa to Adolf Hitler) is filthy rags. I cannot redeem myself, nor can you.
So, if you want a life filled with rage, judgmentalism, competition and self-loathing follow the rules. If you want a life filled with peace, contentment, love and compassion, follow the way of Jesus. You can' t have it both ways. I know. I've tried both.