Explanation

The first blank refers to the intention of the editorial, which suggested a preferable alternative to the current administration; a good word to describe the editorial’s intention toward the incumbents might be a word such as attack or undermine. Of the choices, only impugn means attack.

The second blank refers to claims made against the group that the editorial was trying to support; the actions were inadvertent, so a good word for the blank might be something like supported or proved. Of the choices, the only word that makes sense is substantiated. Since the editorial ended up damaging the interests of the preferable alternative, a good word for the third blank might be something like stopping. Castrating matches this meaning.

Hence options A, E and I are correct!