There is a tendency to ascribe a great deal of power to the Arbitration Committee of English Wikipedia - and of the various arbitration committees, it is the one with the greatest scope and perceived power. In fact, Arbcom has almost no ability to manage the world outside of the pages of the Wikipedia project, and even within the project it can only handle minuscule portions of the activities. It has no power at all to control other websites, can only take action against Wikipedians acting outside of the project if there is an extremely clear and direct link between the Wikipedia persona and the persona outside of WP, and is very wary of taking action in the absence of direct links because many if not most arbitrators and functionaries over the last 8-10 years have been the subject of joe-jobs themselves. I've had to have three separate LinkedIn accounts purporting to be me taken down over the last 8 years, for example; others have had their personal images and names attached to accounts on porn sites, paid editing sites, and a fair number of other unsavory sites - so as a group we can honestly say "there's plenty of reason to doubt" in a lot of cases.
Arbcom is not all-powerful. Even the full force of the WMF can only be turned on to the most extreme cases of harassment; there simply aren't the human resources to address comparatively run-of-the-mill harassment, especially when it's occurring outside the walls of their projects. Not even huge internet-based companies like Facebook, Twitter, or Yahoo have the personnel or the ability to prevent or address harassment on unrelated sites, and they have hundreds of times more "community managers" than the WMF has.
To compare to a non-internet situation: How many police officers would be needed to effectively stop catcalls being directed to women walking down the street? Or preventing bullies from picking on the skinny kid?