how art can build man?

Answer 1

Sustained harmony & perfection gives man a vision of what is possible and thus gives confidence where before there was none.

Answer 2

Art is ok if it complements utility.
Pure art, especially the modern variety, is mostly garbage.

for example - a beautiful building designed by a talented architect is good.

A "Piss Christ" or a painting done with elephant dung.... Bad.
But pieces of art like this are being praised and cherished by the artsy fartsy crowds in NYC and elsewhere.