Actually No, I'm not a warmonger, surprise? Reason being I play on diety with science civs. As I said, I look forward to a non-war game mode. As for the just say so part, my biggest problem is that you can't fight back against an AI warmonger because once you take a city, GG diplo.
Then you're doing it wrong. In my current game, I eliminated an empire and can still conduct diplomacy. Here's how:
After my initial early wars, I waited for my warmonger penalty to die down a bit ("early concerns" completely gone from Incas/England/Morocco/Persia) I DoWed Siam and took their only remaining city - Sukhothai - at EXTREME warmonger penalty in Classical Era. Was immediately denounced by England and Persia (who I denounced right back since Darius had DoWed more than anyone else in the current game, the "I hate warmongers" hypocrite!, and Elizabeth is just a %&#%). All but Inca listed a penalty about my "potential threat" as a warmonger... Inca still only had "early concerns".
Inca had been attacked by both England and Persia, so I hoped denouncing those two would help get Inca on my side... I also decided to GIVE him a surplus luxury I had (got 3 Salt from Sukhothai, so I just gave him one for 60 turns). He remained Neutral instead of Guarded like the other three.
Morocco denounced me about half a dozen turns later, but I chose not to denounce in response - despite the fact he was annoying the bejeebus out of me with his missionary spam on my CS allies. Instead, I bribed Persia (at a cost since he was Guarded, but I had a strong enough empire to bear that cost for 60 turns) to attack Morocco.
Persia went rabid and ravaged Morocco down to 1 city (from 5). England denounced Persia as did the Inca. Then the Inca approached me to join a war against Persia. I requested 10 turns (partly because I was busy shuffling missionaries to undo Morocco's damage while Persia gave me a reprieve and secondly because I was curious if Persia would elimate him).
The Inca jumped the gun and started a war with Persia after about 5-6 turns and immediately lost a city. Darius made peace with Morocco before taking their last city and then my time to join came. I did. First thing I did was liberate two Incan cities (one Inca lost a few wars ago the other the one they just lost) both Minor liberation bonuses. Over the next two turns Inca proposed DoF then Open Borders and were Friendly with no negative modifiers.
My next action was to liberate one of Morocco's cities (at MAJOR liberation bonus). Now I'm in DoF with Open Borders with Morocco... and the warmongering penalty disappeared from England (but I still have enough negative modifiers to remain Guarded with her since I told her to "stuff it" a few times when she made requests regarding CS, where I settle, etc) and even Darius merely dropped to "early concerns".
Between the Inca, myself and several allied CS, we Ravaged Darius down from the number two contender to 3 measly cities (he even gave me his highest Pop city when begging me for peace - a mistake on my part since I dropped to -23 Happiness and had to spend my entire amassed fortune allying with every CS with different luxuries to manage it down to where it'd be -9 by next turn to avoid uprisings).
Warmongering penalties completely gone for the two civs I wanted as allies and I've had plenty of enjoyable action conquering cities, slaughtering units and leaving the landscape dotted with city ruins and pillaged improvements.
You aren't completely hosed diplomatically even if you eliminate a civ entirely from the game if you put forth some effort to repair relations/do damage control.
I now have a solid alliance with Morocco/Inca and have established England and Persia as the "evil empires" despite the fact I'm the only one who's eliminated anyone from the game. Even did so much damage to Persia that England smelled blood and DoWed him to take one of his cities close to her lands, so they won't be uniting against us anytime soon.
And to think, I still have 4 more civs to meet when I get caravels...