in one movie they came for our Women.
More than one movie, bro. In fact, Earth appears to have acquired a reputation as being the truck stop of the galaxy. Aliens are constantly trying to diddle earth people, genetic incompatibilities notwithstanding. Even the Cylons couldn't seem to decide if they wanted to wipe us out or use us as sex slaves (Sort of ironic really...computers using people for sex. I guess it's their revenge for all the internet porn.)
I hate dumb aliens, too. It staggers the imagination that advanced alien beings would master the formidable technological problem of interstellar space travel and still be unable to land with any degree of proficiency. But they crash their saucers more often than a beta copy of Windows.
They also seem to be oblivious to the fact that you can put some pretty big dents in a planet just by flinging rocks at it from orbit. Only the stupid bugs on Klendathu seemed to figure that one out. Better yet, they appear to have worked out how to fling the rocks all the way across the galaxy with astonishing accuracy while lacking any method of space travel. Wrap your head around that.
But most aliens can't seem to hit people reliably with lasers. LASERS, the greatest aid to weapon accuracy prior to GPS. Maybe it's the helmets.
I suppose the main reason aliens in movies are stupid is because otherwise Earth people would fare just about as well against them as Montezuema did against the Spanish. It'd be exciting, but have kind've a downbeat ending.