To me , acting like a wuss means not standing for anything, not being willing or able to assert ones self in the (futile) hope that people will like you if you give in to their every demand (and the hope that you might get pussy, again usually futile)
Being considerate and well mannered is not the same thing.
You're a wuss when you won't go down into the basement because there 'might' be a hobo down there. I haven't used that word since I was nine, so I think this applies.