The relationship between love and fear is similar to the relationship between Higher Self and lower self (ego). The Higher Self is a spark of the Divine, which is pure love; and the ego (while critical to our survival and growth) is often conflicted, and is our primary source of fear.
Real love is not a feeling. It is not romantic or exclusive or reserved only for special people. Within this definition it's impossible to "love" one person while hating another. When you're in touch with the love that is your essence, you respect and honor all of life, not just your own children, friends, neighbors, and pets. A few of the many expressions of love are: joy, faith, acceptance, kindness, forgiveness, altruism, authenticity, patience and peace of mind. Love feels good.
Fear, on the other hand, is the absence of love. Fear is what we experience when we've forgotten who we really are, when we've lost touch with our Higher Self and are clinging---for dear life---to the lower self that we've developed in order to adapt to this world. Fear is expressed in anything that doesn't feel good: insecurity, pettiness, worry, addiction, compulsion, low self-esteem, greed, prejudice, judgement, anger, jealousy, anxiety, depression, etc. Hate and violence are simply fear on steroids.
Learning to distinguish between love and fear will help you consciously choose love more often, and the more often you choose love the happier, healthier, and more spiritually atuned you will be.
You can begin this practice today by simply recognizing that in every moment you are deciding to embrace either love or fear. Forgive someone who has made a mistake, and you've embraced love.Yell at your kids for not cleaning their rooms, and you've embraced fear. It's as simple as that. You don't have to choose love every time, but just watch and see what happens on those magical occasions when you do!