Everyone calling Dawkins a hypocrite apparently doesn't understand, or want to understand, the difference in context between this and supporting someone's right to speak.
Greer was going to be there for an open discussion/debate. This would allow people to question and argue with her if they so choose, as he suggests. It's also not mandatory for people to show up to the talk if they don't want to.
This letter was him complaining about someone giving a commencement speech, essentially having free reign to say whatever the fuck he wants without anyone questioning him. You HAVE to go to this, you don't have the choice. On top of giving them an honorary degree, which WOULD be a direct endorsement by the University, rather than the "implicit" endorsement people were trying to argue for Greer.
There is a difference.