You know, I get why this would be a particularly effective tactic to use on Silverstream. Just based on her reactions to some specifically shaped shadows in “What Lies Beneath”, she’s clearly still dealing with some lingering (intense) fears regarding the Storm King.
And while the idea that maybe this thing she’s terrified of could have been avoided (or might have been less of an issue) if the ponies had intervened earlier isn’t really something anyone can know one way or the other and overlooks a lot of other factors that were involved, fear has never been the best companion of rationality. It really is a perfect combination of unprovable speculation and something primed to make her react emotionally.
But how were they suppose to know that the Storm King threatened them? If anything, Novo just hid her race and didn’t bother to even attempt contact or warning to Celestia about the Storm King. If she did then I get the feeling that Celestia would have assisted if they knew sooner. Also, Novo didn’t even try to fight back or at least made no attempts of fighting back that I know of.
Eh, for it’s worth nobody seems to ever talk to anybody in the world. Stunning degrees of isolation and everybody’s knowledge of the outside world being decades or more out of date seems to be the order of the day here – hell, there’s so little communication inside of Equestria itself that Daring Do can maintain her pretense of not existing and have a huge fanbase who thinks she’s fictional in one part of the country while constantly acting in the open in a different part of the country, because different areas of Equestria apparently never talk to each other.
It’s definitely odd that ponies don’t know what’s going on in their allied countries, I’ll grant you that, but ponies barely know what’s going in their own country.
