This paper discusses a novel kind of argument for assessing the moral significance of acts of lying and misleading. It is based on considerations about valuable social norms that might be eroded by these actions, because these actions function as signals. Given that social norms can play an important role in supporting morality, individuals have a responsibility to preserve such norms and to prevent 'cultural slopes' that erode them. Depending on whether there are norms against lying, misleading, or both, and how likely it is that they might be eroded, these actions can thus have different moral significance. In cases in which the rule 'do not lie', as a relatively simple rule, functions as a 'focal point', acts of misleading are often morally preferable. In other words, in such cases the possibility of 'cultural slopes' can ground a context-dependent slippery slope argument for a moral difference between lying and misleading.