About sexual dimorphism: Many real species have immense differences between males and females. Even more so than WoW characters.
Here's a spider
To be fair, spiders are different from people in many ways, and just because something in nature does it, doesn't mean we should. Additionally, in your own example, it is the female spider who is the much larger, more powerful, and generally less-**** one
. Regardless of random examples, insectival or otherwise, there's no solid argument against a couple additional character choices. The devs obviously feel this way, too, otherwise they wouldn't have announced that they are going to add them.
It's funny that, upon release, there was a vocal number who complained about how the character customization could have been deeper, now SE mentions giving a couple more options, and some people are mad because they feel that everyone should be forced to customize characters based upon their - not the customizer's - personal aesthetic binaries.
Thinking that a character is unappealing is one thing, but thinking that others shouldn't even be able to play them because of that opinion is another problem altogether. I find neither Lalafel nor Elezen particularly appealing, but there is absolutely no reason to disallow other people from playing them. o_O
Regardless of your opinion on this foolish little issue, FFXIV needs all the help it can get. For years and years, many people have been wishing to choose their gender on every race, not just three out of five races. It's not hard to implement, it's not restricted in the lore, it broadens customization, and it responds to persistent requests made since FFXI came out almost a decade ago.
If you don't like the way a race looks, don't play it; let those who like it enjoy themselves. In the same way as, if you don't like a class, you don't play it; or if you don't like a piece of armour, you don't wear it. There's no reason to restrict others just because you yourself have an inarticulate, aesthetic problem with something.
Now can't everyone just go back to being friends again? I hear there's a lot of NMs out there to be attacked! Adventurers unite! *nya*