@Thomas,
There is an ideology, a set of ideas, that many of us associate with the word "feminism". These ideas include restrictions on sexual and artistic expression and a narrative that views a wide variety of social norms according to narrative of men oppressing women.
There is a backlash to this set of ideas from men and women alike. The people who dislike these ideas tend to be the people reject the term "feminism".
In truth, I don't think that the term "feminism" is very important. I don't really care what it applies to.
That being said, calling myself an "anti-feminist" seem to be a pretty effective way to express the idea that I object to this ideology.
Since you agree that all of us are now "feminists" according to the 1970's Websters dictionary definition, and since the people pushing this ideology that I am uncomfortable with call themselves "feminists", it seems that calling my self an "anti-feminist" in a modern context is as good a way as any to make this distinction.
After all, words change meaning and using the currently understood meaning for any given word in a specific context is not unreasonable. I call myself a democrat (that is a lower-case 'd' democrat) even though I don't support a pure democracy. And I call myself a "liberal" in an American context even though I don't meet the European definition by any stretch of the imagination.