Since Clare Hooper has done an outstanding job of summarizing what's happening there, I might as well just steal her summary wholesale:
A very, very brief summary is that the entry on Wikipedia about Gamergate has been the subject of weeks (running into months) of edit wars. It culminated in a decision from ArbCom, the highest user-run body of the site, to ban the five editors who were trying to prevent the page from being rewritten with a pro-Gamergate slant. According to Bernstein’s analysis, sanctions were also applied against some of the pro-Gamergate accounts — but only against a few accounts, and throwaway accounts at that.
Basically, Wikipedia has decided to hand over the keys to the henhouse to the foxes.
I myself have been contributing to Wikipedia for ten years. However, this is just too fucking much. Either the ArbCom is suffering from a massive case of the stupids, or the ArbCom is carrying water for the 'gaters. It doesn't matter which, because either one is reason enough for me to stop contributing.
So that's what I've done. Unless Wikipedia shows a sudden rush of good sense and both completely reverses this decision and issues a sincere apology that actually acknowledges wrongdoing and offers genuine contrition to the many injured parties involved, I won't be back.