最好的反擊就是對人家的建議作個評判，站的比對方高一等，讓對方體會一

下你的感受：so you should say:  your suggestion is not too bad, but I think it is not (even)  a good point for my case, I think I know how to get it done better, thanks anyway for your suggestion. 具體情況應該要看你本人的水平，如果你是高於對方的， then you can even talk to your manager at the same time:  I think you can assign him or her( the person) more things to do  (  it means the person has nothing to do,吃飽沒事幹，多管閑事)