Its the meanest thing you can do. Not only is it deceitful and hishonest, it also robs the guy of his trial and error learning process in sex- if nobody tells him hes not doing it right hell never learn
And it doesnt even have to hurt him! just phrase it right
dont go - I find it boring/it does nothing for me when you...
but go - I really like it when... It turns me on when...
Tell him what youd like him to make sex like.
its that fucking easy. Its so mean to fake enjoying it. the thought of it pisses me off.