1. If they are cold because they are afraid to commit / trust, extended demonstrations of affection or support can change them.
2. If they are distant to you because of ideology, such as Islam calling for hating the infidels or death to homosexuals and atheists, trying to be loving and supportive is dangerous and deceptive. It isn't an emotion that you can change, and regardless of their feelings, they have social reinforcement to distrust you and disdain you and justify the negative emotions.
3. If someone is a psychopath and unable to truly empathize, trying to love them opens yourself to manipulation and abuse. Don't try to change them.
4. If someone is a sociopath with poor emotional control, they need psychological counseling and maybe medication, but they may be directed to useful actions in society and healthier relationships with others. If they physically assault others, though, and only seek to justify it, don't try to change them by "love" - leave.