He seems to think that you need physical proof for a mental abstraction and that mental abstractions can't exist without physical proof.

Er, I shouldn't have to remind you, having typed the words so many times, that I neither seek proof for myself nor ask for it from others.

If someone believes in a God then to them it exists. If it guides them in their decisions, lifestyle and deeds then that is tangible proof that their God exists.

This is completely at odds with your comment above. "Tangible" means physical, and you just told me I wasn't to seek physical proof for abstracts! OK for the believers you so valiantly defend, then, but not for poor ol' Steve! Thank goodness I wasn't saying what you said I was saying anyway! :-)

In any case, your second quote is a classic case of begging the question. Nice one!