I'd like to see your scientific understanding. Does it have to do with the James-Lange theory, or the two factor theory, Canon-Bard theory?
Hell you never know, your scientific understanding might allow an argument.
Love: Chemical reaction to another, with the added want to engage in reproductive measures.
Happiness: dopamine being released more in one situation, than an other.
Anger: Fear of the unknown, for example the student with the black bag. During 1967, a student decided to wear a black bag for the whole time he was in said class, no one saw his face and as such, people became afraid and angry in his presence, once he sat near a girl - if memory serves me right - and she screamed for him to be removed. Of course, after a while the students in said class started to call said bag 'their' bag and as such making it seem as somehow, he had some way confirmed to be like them, of course it was simply them projecting their own thoughts onto the student, he said almost nothing at all.
Then there's my own personal theory.
Anger: Weakness, I say that because we're all animals, and as evolved as we are.. we ain't perfect just yet. During my time in high-school, I was in base with a number of mentally challenged students. None of them went out and mingled with the main-stream students, and as such, the ones who thought themselves 'normal' reverted to act like a pack of wolfs on the lowest able member of said unit. To start with, there was child with speaking problem, and a environment problem, he couldn't handle a normal classroom setting, the 'wolf' children knew this and set about each day to bring this child to tears.
That theory could possibly be adapted with the first one, the people in the class room with the black bag might have seen him as some kind of weaker being, and as such went on the attack when they were left alone with him. But when other's decided to pick up the subject, they became rather defensive. Same goes for the children, if a main streamer decided to pick on one of the kids inside the base, they'd join together to defend said child, even if they had been picking on him themselves.
And just to be a little clearer on the love. We're social creatures, or the majority of us are that. We need others in order to keep us just 'right. With that in mind, to bring yourself closer to someone, - in order to make sure you always have access to the social aspect of your humanity - so that in time these bonds simply grow which turns into 'love'. Though, cut the head off the snake, and the body withers, as they say. Or, if you don't water the plant, it's buggered.
So yeah, love is understandable, at least in my own eyes.