最好的反击就是对人家的建议作个评判，站的比对方高一等，让对方体会一

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. 具体情况应该要看你本人的水平，如果你是高于对方的， 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,吃饱没事干，多管闲事)