First off, love is not a feeling. It is a choice manifested in actions. Second, purposely fomenting hatred towards others will just make a habit of anger; it will not "spend" the hatred and heal the hater. This makes no sense.

"Repressed hatred can lead to many physical and emotional ailments."

A claim like that really shouldn't be made without supporting evidence.

"By learning to release your hatred towards those who deserve it, you cleanse yourself of these malignant emotions and need not take your pent-up hatred out on your loved ones."

This kind of thinking was the basis behind the venting therapies that were popular in the '80s and '90s. Research outcomes contradict the venting hypothesis. Aggression is effectively habit-forming and is not therapeutic.

See:
Bushman, B.J. (2002) Does venting anger feed or extinguish the flame? Catharsis, rumination, distraction, anger and aggressive responding
http://www-personal.umich.edu/~bbushman/PSPB02.pdf

Internet Ranting and the Myth of Catharsis https://www.psychologytoday.com/blog/unique-everybody-else/201303/internet-ranting-and-the-myth-catharsis