When it's part of a production, usually there isn't an argument. There is a personal bar that the production would need to cross before fan-service becomes this unsightly thing and, I will admit, my tolerance of that is rather high.
The issue? There is quite a bit of official work with the Nanoha franchise that isn't tied to any production, not the movies, not the audio drama's, not any of the ongoing manga's... and anime has been sparse for years.
Do I enjoy the hell out of it? Sure.
Is it bait? Yeah, it is. Most of that work has almost no excuse to exist otherwise. It's a thinly veiled attempt to keep some focus on the franchise without actually doing anything. And here is the thing, it's been working.> Yuri bait is like Kumiko and Reina, that in the anime had moments hinting at something between them just to get the attention of the yuri fans, but at the end both girls have male romantic interests instead.
Ok, that is just... bad. I mean, I have seen things like it several times before and I can't help but wonder if the writer engages in any relationship if they are just going to push in a partner on a character just for the sake of it.
And this effect yaoi/yuri relationships as much as het ones. It's just stupid romance writing.