I am not a huge sci fi fan, but like Star Trek TNG...
watching an episode of the borg attack on earth I came across a thought that bothers me.
In all the sci fi I have seen where inter-planetary travel happens, and alien races exist Earth is the center of the human race (obviously). generally it is a hugely developed planet, and many ships in orbit.
I almost all sci fi things I have watched there are weapon technologies "banned" by the human civilization because they are immoral, or whatever reason.
wouldn't you as a civilization use any and all weapons as a last defense on your main world? wouldn't you have moon based, and other huge defensive emplacements in place in case of a threat?
it makes no sense for the "bad guys" to use more powerful weapons the "good guys" know about but refuse to use (other than to create artificial drama for a story).
this has bugged me for a long time I just never put a real finger on it. maybe thats why I don't usually like most sci fi, artificial drama written into the story that doesn't make logical sense,