The most you can say about democrats is that they passively object to fascist ideology, but they never do more than throw procedural obstructions to fascist momentum and legitimize reactionary grievances by repeatedly affirming xenophobic anxieties about immigrants and minorities.

The reason leftists argue that both parties operate under the same fascist framework is that they both prioritize a failing capitalistic system over radical socialist reform, and so will (either by choice or because trying to preserve failing capitalist systems leaves them without a choice) bend to reactionary populism and abandon socialist populism.

“democrats are better than republicans because they oppose fascism” is really only true if you ignore the common consensus among political theorists that fascism is the end product of deteriorating material conditions and the tendency of capitalist systems toward self-preservation. So long as democrats deny the demand for popular socialist reform, they are nothing more than the moderate wing of the same fascist uni-party. To be truly oppositional to fascism they need to address the contradictions in their own political framework, or else be constantly pulled rightward by the same reactionary forces acting on the right.