how does this prove christianity is valid?
This wasn't meant as a proof of the validity of Christianity. It was simply a statement that there are specific instances where Christianity does some good in the world.
People are absolutely clueless how much charity and selfless help Christians around the world do to make this world a better place.
Or church has raised over 20 grand to help people who lost or hand great damage done to their homes in a recent flood. This is not to mention all the donated items as well as offering up their homes to help make this transition period more bearable.
This is just one church that has made a big difference in other people's lives.