Earlier quoted context omitted.
By adding "morally" it enforces questioning one's own principles in support of the thing. Without "morally" it's dismissable nonsense (ie. bullshit). With "morally" it requires pulling at strands that make up our world-view. It's not necessarily a bad thing to question one's world-view on occasion, but causing that level of fundamental questioning, for a comment that would otherwise be easily dismissable, is gaslight…
Personally I think the repeated part of the gaslighting definition is really important (and the implication that the repetition is conducted abusively). Otherwise you'd argue that any dialog that causes one to question one's world-view is gaslighting, and that's simply not true under the colloquial use of the term. If I make a statement that killing is not justifiable even in self defense, and that causes you, who be…
For example, repeatedly arguing that you think the idea of unchecked ownership of assault weapons is a stretch too liberal of an interpretation of the 2nd amendment, and that it's crazy to think it's okay for anybody to own one without training, and that you think it'd be a good idea to limit gun ownership and require mental health checks and registered firearms lists of trained individuals, and even that you think it's immoral to allow such easy access to acquire devices that make killing trivial, because it puts too much responsibility in the hands of civilian organizations to protect people from maniacs, which they clearly can't do at scale, and even to go so far as to argue they're insane to think otherwise, is not an instance of gaslighting gun owners or rights advocates into thinking their worldview is broken and in need of an update. But by the casual interpretation, it is, since you're arguing to oppress the liberty of some group of people on practical and/or moral (designation doesn't matter, anything that causes them to question their worldview) grounds.