Is this true? Aside from the fact that getting "your body language in order" is easier said than done, it would be pretty easy to do an experiment to test this hypothesis. You could approach one hundred women in this way and see how many responses you got of each of the following nature: active hostility, passive "please go away" politeness, friendliness, perceived actual sexual desire. You could even get, say, five different men from different quintiles of physical attractiveness to see how it varies.
P/S/A: There are single sentences which can create life-changing amounts of difference.