is love pure and can it change anybody???

The difference between love and a nuclear weapon is that you can miss with a nuclear weapon. Purity is a matter of opinion. I think anything which engages on so many levels isn't that simple. It's definitely not easy to define, and certainly not with a word which can also be used to describe household products and the state of your plumbing. If by change you mean become obsessive, change all your priorities, and in some cases become a much better person, yes.