A responsive filing is req'd (to avoid a default ruling) whenever a pleading or motion is filed, but there's no "likelihood of success" test in order to file a pleading or motion in the first place.
In other words, a party can file an action/motion and trigger responsive filings as a matter of course. In general.
"Stating a case" is a term of art. One can file a claim for something, but whether that claim can properly be brought depends on myriad things: standing, legal recognition of the nature of the claim, source of the perceived damages, etc., etc.