(I don't personally egg on drama, or wish it to be created, or anything like that. But I do have a prurient interest in drama, even if I agree with WisCon's mission and think most of these characters weren't great people)
Jim Frenel attended WisCon in 2013, and was alleged to have harassed another attendee.
Jim Frenel decided to attend WisCon again in 2014, which some people thought was inappropriate. Much drama ensued.
Elizabeth Moon was initially invited to speak as a Guest of Honor. However, this blog post of hers was discovered, which talks about the so-called "Ground Zero mosque" (AKA Cordoba House, AKA Park51) with comments like this:
Not only were the attackers Islamic--and not only did the Islamic world in general show indecent glee about the attack, but this was only the last of many attacks on citizens and installations of this country which Islamic groups proudly claimed credit for.
Once this blog post was resurfaced, she was uninvited as Guest of Honor. Many people wrote blog posts about it, but this is a good summary.
(for what it's worth, Elizabeth Moon eventually replied to the incident by way of an article that appeared in NewsOK)
A woman (named Rachel Moss) attended WisCon, took photos of other people, and then posted them on the online humor forum Something Awful alongside snarky commentary.