Taste the diffidence
I think he makes it very explicit what he thinks of the rhetoric of the NF in the song. He basically allows them to condemn themselves out of their own mouths. Quotes like wanting the day to come sooner, settling scores, showing what you're made of are all poking fun at the ridiculous machismo of such organisations. Anyone who thinks Morrissey is being neutral when they hear those lines doesn't know much about Morrissey's aesthetic or his general views on gender politics.
He does explicitly mock the NF but as I said one possible reading of the lyrics is that the speaker is essentially a nationalist who thinks the NF is silly. (Here in the States I've seen many racist/nationalist idiots whose hatred wasn't diminished just because they also thought the KKK was a joke.)
And a small but important note: in a thread where people are hanging a lot of meaning on quotations marks ("England for the English") I'd like to point out I encased "neutrality" in quotes. I don't think he is neutral either. But as you yourself say, Jones, to understand how and why the song isn't neutral you have to "know about Morrissey's aesthetic" and "views on gender politics". Which underscores an aspect of something I said above-- what you, Morrissey and I see in "NFD" isn't the same as what the rest of the world might see. While we have a right to say, "Who the f*** cares what the rest of the world sees?" to some it might not be so easy to dismiss.