If you consider it just as emotions, than it makes sense to say that indifference is the opposite of love, but there is more to it. As I have pointed out before, thoughts carry energy and that energy, like all energy, does work. And emotions give thoughts a boost of energy so that thoughts that are backed by strong emotions will carry much more energy than thoughts without emotions. And that additional energy means the thoughts will do more work.

    Since love is a positive emotion and thought and carries with it a sense of caring and giving, thoughts backed by love have a lot of positive energy behind them. That positive energy will benefit whoever or whatever those loving thoughts are sent to. That positive energy can help a person overcome an illness. It can help an injured pet heal. It can help a plant grow. It can help water form attractive and symmetrical crystals when frozen (see the books of Dr. Emoto).

    On the other hand, hate is just as strong an emotion as love and carries with it ideas of revenge, of harming the person or thing that is hated. Since, just like with love, the thoughts transmitted under the power of hate will carry negative energy that will do harm to those it touches. It can make a person ill, or make an illness get worse. It can cause animals to behave aggressively. It can stunt the growth of plants or cause them to grow misshapen.

    Indifference though is neither positive or negative. If someone is indifferent to a person or an animal, he doesn't even acknowledge their existence. If she has no emotional response to that person, animal or thing, than any thoughts sent to it will have weak and fairly neutral energy flowing with it. This weak energy will have no particular affect on the recipient, unlike love energy or hate energy.

So the opposite of love is hate, not indifference.