Nothing overly evil or impossible about psychic vampires.
They do exist. But lets be clear, it is an action, not a thing.
You are not evil. There is not some underground niche of vampires that you will be tied to. There are clubs for the sort of thing, but that is not a necessity.
People do it all the time. Psychic vampirism is simply the act of draining energy from something else. Sick people do it, angry people do it, sad people do it. It happens.
But, the skill can be learned and the technique can be increased.
That being said, it's not exactly the reliable. There are other methods of obtaining energy, and purer energy.
If you want to cleanse an object, the easiest way to do it is to first drain it. After which you infuse new energy into the object.
Healing can be done by sending intense forms of higher energy. But it can also be done by first removing bad or dull energy.
Breathing energy is also a form of psychic vampirism. This happens when you breath in one energy and breath out another. This is also a very good way to align things or people together. It is actually a very loving relationship.
Don't let words fool you. The act isn't as evil as it sounds.