The practice and ideology of sysop vandalism unites the Wikipedia sysop power structure as their means of excluding outsiders and those whose views are unacceptable or alien to them.
The basic method of sysop vandalism is simple: under the guise of "protecting" or "neutralizing" or "enforcing rules" which are not part of the GFDL, the sysop power structure damages the GFDL corpus by undoing improvements or corrections made by the trolls - in the most extreme cases they employ ad hominem delete as well, making it impossible for non-sysops to read text and evalute it for themselves.
By doing frequent damage to the corpus they render it less useful and less reliable, and discourage those users who actually care about its improvement. As those depart, the overall quality of editors and contributions remains low enough that the founder/owner and his cronies continue to retain some authority. Were they to cease sysop vandalism then better qualified people would remain and win arguments and allies to their side, and the founder and his cronies would soon be swept aside. This is exactly what they seek to prevent by doing the damage. Since there is little or no penalty for GFDL violation, GNU having given up its GNUpedia and failing to enforce the license (one of many problems with free software and open source models), the vandalism proceeds with impunity.
An interesting test of the concept is to see if a member of any sysop power structure will acknowledge that any sysop has ever used any power to do what can be described as vandalism. It is so basic to their command hierarchy to deny that power is ever abused that they will deny it, and will always deny that there is any such thing as sysop vandalism. By contrast, people not involved in such a power structure will readily acknowledge that some people with power to prevent corrections and improvements will use it for narrow and personal purposes, or more obvious and overt political purposes.
Simple denial that sysops ever do vandalism is enough to create sysop vandalism by providing cover - once one has the power to do the worst damage, suddenly, there is no scrutiny.
Anarchopedia:Itself disables sysop vandalism largely by letting any user see and restore the text of any deleted article, and by not using the power to block IPs of users opposing the sysops - this power is reserved only for vandals such as spammers who can be objectively identified. Devotion to the GFDL corpus and its improvement, over and above the greater glory and control freakery of any one GFDL corpus access provider, plus negative anarchist assumptions about power networks and groupthink, further prevent any abuses from being glorified.
Permitting and encouraging sysop vandalism is the major way in which Wikipedia violates GFDL.