"Is this racism? Could it be that it is impossible for gaijin ("barbarians") to create bonsai? That we must be doing something else, but it's not bonsai because we are gaijin?"
It goes to show that snobbery is universal and a people famed for mannerly reserve can be cloddish oafs too.
I find the idea of Japanese folks living in Austin laughing at something because it may not be "Japanese" enough, rather amusing. Were the people doing the laughing and pointing running about in kimonos and slatted shoes? Or were they wearing Ralph Lauren jeans and cowboy boots?
So much for cultural "purity."
Ignore them. Their behavoir suggests they know nothing of their "native" culture, or they have forgotten that humor and respect for others that are hallmarks of it.