You should try to explain why you think so. Do you think so because he can sound overly fanatical about it all?

For some reason or another religious fanatics tend to be always a million times worse. They actually kill to 'prove to you their right'; did you know the penalty for young children to not believe is death in many Islamic countries? This is true for many more religions and/or sects all over the world and they all happily ignore that there's no free choice to believe what you want. This effectively means people are forced to believe whatever they're being told.

I'm pretty sure Dawkins used to be quite open minded. Perhaps until his very own words were used against him in all kinds of very out-of-context ways. Darwinists are often said to be racists, pro-eugenics and so on, which is clearly nuts.

I'd say some of his fanaticism is the natural result of all that.