The central point of the article is that non-GPL licenses are not wrong, and a GPL exception is no worse than a non-GPL license. I think this point is very clearly spelled out.

I think it is very clear that he is saying, some software wouldn't be free at all if not for dual licensing. So if dual licensing allows more software to be free, then it is good.

Quite the contrary [1]: The assumption that proprietary software is "immoral", "unethical" and "evil" is very much the heart and soul of the Free Software Movement.

To say it's not, sometimes, would contradict this assumption and make it invalid. So, it would indeed kill him.

[1] Strickly speaking, he's OK with non-GPL software as long as it's "free" according to his definition of "free".