It is, if you're very, very careful about it... If, for example, people are looking for a polite way to do a sort-of rude thing, you should provide your critique in the form of an otherwise legitimate answer:
So something like 'Don't, no way that's possible' isn't a good answer here.
An answer that states 'In my opinion, this is the politest IPS approach you could take, and it may backfire like so and so, so it may be better to just do nothing' might be a valid answer, especially if you can back it up by experience/sources or a good and solid reasoning...