I know fascists do this, but doesn't everyone kind of? If you don't think your enemy has strengths then they're not worth being your enemy and if you don't think they have weaknesses then opposing them is pointless.
edit: I guess one difference is fascists pick enemies that genuinely are powerless, but that doesn't really seem to line up with the original claim
No you're correct. Eco wasn't employing a material analysis of fascism, but rather trying to approach it through describing its ideology which is why his description of Ur-fascism is incredibly broad, vague, and easily challenged. To your common liberal Ur-Fascism seems like a radical idea, but it rapidly breaks down under historical scrutiny unless you dig yourself deeper into the hole of liberalism and embrace ideas about "totalitarianism".
Contrast Ur-Fascism with a common Marxist definition of Fascism such as "when the bourgeoisie recognize the unsustainable of their situation and begin employing more overtly authoritarian measures and exralegal formations of the petite bourgeois and lumpen to crush the communist movement", or perhaps another typical materialist description such as "when imperial modes of control are employed in the imperial core". These offer concrete, universal descriptions of fascism. While they might require knowing some different jargon, this theory is crucial in understanding how to struggle against fascism and to destroy it for good.
I don't know the specifics of Marxism that well to be honest, but I thought the point of material analysis was not to completely discard the idea of analyzing ideology but to recognize it as arising from material conditions.
Okay so a couple of things:
I brought up Umberto Eco because my mind immediately jumped to him but the specific question you first asked about how an enemy can be weak and strong at the same time was specifically put forward by an American political scientist in an article called Fascism Anyone? which was calling the Bush regime fascist. This was probably derivative of Eco's essay Ur-Fascism which is why I got them mixed up, though the critique largely remains true.
You're correct about material analysis but nowhere in either piece does either author describe class struggle (maybe with the small exception in Eco's sixth point but otherwise it is absent) or the crisis of capitalism. For instance, lets look at Eco's second point
Now to be fair to Eco, his whole idea is that fascism coalesces around these ideas and is not necessarily defined by or limited to them, but in this instance he specifically ascribes rejection of modernity to the arise of political liberalism in the American and French revolutions and calls rejection of capitalist relations a "disguise". Now what seems more likely? That the Nazis wanted to return to the political relations of the 18th century, or that they recognized urban industrial capitalism sucks and wanted to go back to their romanticized version of the past as peasant farmers?
As you point out in your post, anyone with enemies will consider them simultaneously weak and strong. Doomed to failure, but they'll succeed if we don't act. Idealists like Eco say that plainly contradictory stances like this are what people (or fascists specifically) look for in political movements, materialists say that this is a product of the experiences those people have and how they've come to understand the world.