A frequent visitor in contemporary social discourse is the objection to the practicality of the idea. Once a radically different idea is brought forth to challenge the existing norm, the last resort is invalidating it by making it too ideal, impractical and an impossible utopia. Such a phenom can be observed against Communism, and sometimes Feminism, frequently. For them distributing wealth and resources equally and abolishing private property will never happen, therefore ought not to happen. While there are strong critiques against communism, and as a person advocating for such critiques, the aforementioned argument is philosophically immature.
A practical scheme is either one already in existence, or a scheme that could be carried out under the existing conditions; but it is exactly the existing conditions that one objects to, and any scheme that could accept these conditions is wrong and foolish.
Oscar Wilde
For something to be practical, it must be aligned with the social norms of the context mentioned. By engaging in a discourse about a novel idea, perhaps completely against the old one, one is willing to debate the feasibility of existing circumstances. By appealing to practicality, one assumes the existing circumstances to be better, if not the best, essentially resulting in a fallacious bad-faith argument.
Furthermore, such arguments occur in the moral context. A question of ought needs an answer. What ought to be the right economic system, or so communism asks. What ought to be the way to treat the sexes, or so feminism asks. And so on. Repudiating them due to impracticality becomes an example of the is-ought fallacy. The ideal action is derived from what has worked, and more importantly what will work as a result of the current state of affairs.