Those kind of threats can be defeated with a simple weapon or a strong enough fighter, threats like racism can't be defeated in one fight like that, and it could be pretty much anyone, anywhere.
As a person who has and still deals with varying degrees of racism, I can tell you that yes, it is a problem well built into the institutions and social relationships of a certain part of society, however, if something on the scale of fantasy threats like the Chitauri invasion, the Reign plot, or the worst kind of threat in the form of Thanos hit earth, suddenly
every person on earth would be engaged, suppressed, hurt or killed and just as quickly, tribal matters (or those who weaponized race in society) would seem small in comparison. People are still having to
live through mass death/destruction (and its global consequences) before a "punch" can solve anything. The point being is that the showrunners' statement lacked perspective in trying to make their issue of the week (immigration / xenophobia) seem like the end-all Is Here Now, but those matters do not just happen and explode into the end-all overnight (as the tone of Supergirl's dialogue tried to sell), no matter what some politician says or incident(s) unfold.
Since society has always fought the purveyors of racism in one way or another (for centuries in the U.S. where
Supergirl is set),
audiences know that in reality, the situation just did not creep up and overwhelm when in fact, certain people have dealt with forever--handed from one generation to another like some terrible heirloom.
That said, in fantasy fiction, the fight against racism / xenophobia works in a more compelling / realistic way, when its established that its always around and as mentioned earlier, built into up-front, social relationships and institutions, as that is the gnawing, bleeding, face-slammed-into-the-wall problem that poisons lives
every day, (as seen in
Black Lightning's Freeland with its police abuses & A.S..A. manipulation issues) as opposed to writers trying to jump on the "Trump vs. immigrants" stage as if that is a threat to all life on earth that landed overnight just to be topical.
Supergirl as a series introduced the xenophobia or anti-extraterrestrial (Luthor / Cadmus) sub-plot seasons ago, but in order for it to have been truly effective, I think its clear the series needed writers who seriously understood the complexities of subjects like race in America (again, where the series is set), and that selling it as an important, on-the-street issue required more characters--main characters--who could speak to how that treatment shapes or hurts lives on an daily basis.
As it stands, that opportunity was barely touched on--well into season three--by James, but he--the living embodiment of victims of built-in discrimination--hardly said a word about, or experienced any serious issues with it over said three seasons. Then, there's J'onn: he's made his comments about xenophobia before, but its always in the surface-y,
"One to Grow On" way, or its here today, gone tomorrow as in the M'Gann or Lyra storylines with no lingering consequences for the
regulars, as it should be. Instead, we had Supergirl running up acting as if this is some new discovery of a super-bomb set to go off...yesterday, and that speaks to the showrunners mishandling the subject where it could have been explored as a paced, layered character development issue with James and J'onn all along.
This is why I hope that whatever episodes are already shot, the plot of James becoming the Guardian again, is arrested and stands trial is among them, so at least it might offer concerned audiences the hope that showrunners dealt with the issue / of society's treatment / perception differences between James and Supergirl (who was a vigilante before joining the DEO) to hit home a real
human example of mistreatment (as a point of identification for audiences) based on racial origin. Then, you'll have a greater commentary on hated not just limited to immigration, but that ancient evil overall.