well, i personally dont see a difference between fürst and any other korean, US or spanish spammer.
so why should i block any other ISP's AS/traffic? the collateral damage might be too big and does not justify the filtering.
anyway, i dont like spammer and i don't like fürst at all. i cannot understand the reasons of EWETEL to not react on it, because it's a normal abuse case where they risk to get on blacklists which can cause them more damage.. but anyway, thats their risk....
if you think to put the whole AS9145 to the swinog antispam list we might consider to not use anymore the list, because we're having then a sorbs-a-like effect which i dont like ...
but i'm not the decision maker in our company, so this remains a personal view ;-)