[PeterisP]

If a proposal is bad because the idea has flaws, it's appropriate to express disapproval of the idea.

If a proposal is bad because a decent idea is lazily written (as the original post states), it's appropriate to express disapproval at the person - if the only thing that was needed to change in order to make this proposal better was the person's attitude (do your homework properly before submitting the proposal instead of wasting everyone else's time), then it is constructive to target that attitude.