Seth, you're mixing attitude with reputation. They are 2 separate things.
If you load up military, declare war and go arsekicking around the other civs will have a bad attitude toward you. Au contrair, your reputation stay intact. They can hate you to death and still think of you as honourable. This means that you can sign MPP, ROP, or buy techs for resource, luxuries and gold per turn with the civs you are at peace with.
But if you: 1) cause a premature end of a trade deal; 2) declare on a civ with a MPP; 3) exploit a ROP; 4) attack a civ with a peace treaty signed less than 20 turns ago; 5) declare on a civ while you have troops in its territory & so on... your reputation is ruined forever. No more techs payed in 20 turns. No more ROP or MPP unless you shell out a tech or a large amount of gold immediately. Alliances more difficult. Trade deals more difficult, and so on.