You're absolutely right that it's totally up to him and he can act the way he likes, but I think the point of the article is that if you're claiming that open-source is a "community" endeavour, then perhaps being a giant asshole isn't the best means of accomplishing that end. He is discouraging potential developers from wanting to work with him for exactly the reasons you mentioned: it's not a job, there is no pay, he's not your boss. The last thing I want when volunteering my free time is some guy belittling me. As has been mentioned in this thread, there are ways of accomplishing the same task while being a reasonable human being. His ego and entitlement are justifying his behaviour and it's bullshit.
I'd say open source on the whole is a "community" endeavor, but individual open source projects are not necessarily. There are countless projects that are a single author who accepts bugfixes here and there but in general it's a one-man show.
The linux kernel is like that: it's Linus' project that he lets some people help with. It's a dictatorship, largely ego-driven, and he has the last word on any philosophical, design, architectural, or even political decision. For better or for worse.
