the only time i have seen bb's shatter is on them crappy perforated steel glasses (i was wearing the glasses, shot at point blank and i did pull a pragment of bb out of my eye), in a crappy barrel (long story), and when one clipped a sharp edge. i have never seen or had reported to me that any of my shots (i use blasters), have shattered.
lets face it all bb's can and will shatter.
i have never heard of any site banning blasters (until reading this). i could go on for days defending blasters, or i could just ask if the site sold them before the ban? if not, it could be to corner the market etc.
in any case, its the site owners rules etc.