I actually hope that choosing one dialogue option doesn't erase all the other options.
Depends on context, but most likely it will. The point is that if you befriend person A, you make an enemy out of person B. Meaningful choices by definition means that your choices have consequences, and most likely result of this is that other options become unavailable. I very much like this, and it improves replay value in addition to immersion. I seriously HATE the modern trend of "I want everything without paying anything and without consequences".
For example, if you decided to ignore Stouts tampered credchip in the flatheadbot mission and not help her, you make a friend out of Anthony Gilchrist and most likely an enemy out of Stout.