It is possible to challenge the assumption without challenging the poster personally. Changing 'you should' to 'I think if I were in your situation' provides the same information without the personal attack. Anther useful phrase is: 'it's hard to argue with the numbers' In this case, its the numbers fault, not yours or the person you are responding to.

Please remember that some of these individuals have never posted on a forum, and have not learned to NOT take things personally, regardless of what is said. It is very frustrating when critical information is being ignored, but shouting is not always the best response.

Maria