This is a very nice philosophy, and one that seems inherently attractive once you get past all the stereotypical hippie "peace and love, man" images and associated cynicism that accompany it. We are attracted to simple solutions for complex problems, and you don't get much more complex than human relations across the whole planet. If we somehow could get everyone to feel better about themselves, and consider others more in their actions, it's likely the world would be a better place.
This is probably a good idea that, like communism, just doesn't work once you factor in the complexity of human behavior.
However, I'm here to tell you that on a local level at least, it definitely doesn't work. Or perhaps it works too well. Decide for yourself.
The point where it all falls down is that a significant number of people are starved for affection. My own experience tells me it's at least 50% of people, possibly up to 75% or more. I'm probably one of them. If we relied on affection for nutrition then there'd be a world-wide famine of epidemic proportions, and most of us would be lying on our death beds with swollen bellies, covered in flies.
So, you tell somebody like this that they matter. That they are a special person, lovable and worthwhile. That is a powerful emotional high. It's like a drug for them. They want more. They crave more. They can't resist it.
(Actually, it is a cynical world and the most likely response is skepticism, wariness and distrust. You might get a laugh, a dismissive comment, sarcasm. Lets assume that you can project your sincerity.)
They want more.
They want more from the only source they've found it: you. They'll find a way to be around you. Maybe you'll date (if appropriate sexes) — but do you really want a relationship where you're only valued for this one thing? Or worse, a relationship where one day your realize you're merely bartering compliments for sex? Or will you just give, and give, until you're sucked dry and have nothing left. How much have you got to give?
This also gives you significant power over the other person. You're their dealer. They need you. It's an easy position to fall into abusing; you may not even realize that you're doing it. If you can take, with no consequences, are you strong enough to resist?
(This write-up brought to you by "real life experience", together with "I'm feeling cynical today.")