Dawkins has a long standing policy of not debating various sorts of wackos. "Calling him out" on this would obviously be seen as pointless trolling and spamming. Kicking someone for that is not quite the same as censorship.
WLC may be a typical apologist, but he's not a wacko, certainly no more a wacko than other people Dawkins has given the time of day to. Yet, when asked to debate him, he claims not to have the time. It's not really surprising that some people are led to believe he's being evasive.
And there's nothing wrong with criticising someone for refusing to take on the more difficult arguments and opponents on the other side. It hardly constitutes 'trolling,' ill-defined though that term may be. And of course kicking someone for spamming and trolling is one thing, kicking them for merely criticising someone is another altogether.