This is so obviously untrue that I find it difficult to believe it would take you long to come up with counterexamples yourself if you tried.
What is your counterexample?
This fear likely constitutes a more effective mechanism for turning large numbers of people away from genocidal hatred of various forms of "otherness" than rewarding positive behavior or making a reasoned case because it scales better. So the claim that fear of otherness can't be counteracted by other fears seems implausible to me.
This is true, but it is also true, increasingly so, that [accusations of "fear of the other" as being the underlying motive behind those who simply have genuine concerns] is being used as an incredibly effective rhetorical technique to shape people's thinking.
There is no flip side to that where fear of something else would counteract that. Many of those things that are influenced by a powerful emotion such as fear are like that, they only work one way or at best are very asymmetrical when you try to imagine the opposite.
So it definitely explains something. Just look to history for some pretty good examples of the end results.