You may certainly make the argument that a sizable guerilla urban force could perform outside their weight class against a federal army. However, it makes no logical sense to assert that most liberals buying guns do so under the theory that they will organize together against their government, nor that they do or should believe that this piece of military wisdom would work out for them.

I.e. it's obviously reasonable to believe that private firearms cannot stand up to the federal government, regardless of whether it is the case under theoretical conditions.