Whether Nihilism is an attack upon other beliefs, it does usually accomplish the questioning of beliefs since it is the negation of certain beliefs. As this negation, people who perceive beliefs that they have held coming into question may become defensive and perceive an "attack" upon their beliefs when, in actuality, such a judgment is purely subjective.
Nihilism is an idea that can make people want to attack others, perhaps. Nihilism is the idea that there is no basis for any sort of belief, that nothing has any meaning. Such an idea can clearly be used to attack the beliefs of others.
However, so can any other belief, right? Christian ideas can be used to attack nihilism, for example. So I am not sure why nihilism would be any more an "attack form of an idea" than any other idea would be.
I don't think that the discussion was about comparison between various forms of attacks, but it was about "nihilism - as a form of attack".
In my opininion, since nihilism is destroying the essential values of human existence, by denying everything, could be a powerful form of attack.
Nihilism can represent a form of attack on a particular idea, movement or group, however, is a philosophical position that can be adopted by a person. Cultural movements such as Dada or Futurism, among others, have been identified by commentators as "nihilistic" at various times and contexts. Often, this means that the accuser's beliefs are more substantial and closer to the truth, while the beliefs of the accused are nihilistic beliefs and by comparison, have no value (or are simply considered destructive by reckless).