The trick is (I believe)
a. Change the number in top of diplomacy.txt to # 3
instead of # 2 . I believe 2 is a mistype.
b. Change the various incursion/invasion numbers (these are per-turn regard numbers) in
DEFAULT diplomacy to 0. Thus, AIs won't hate each other for minor actions.
c. Add more meat to the MAKE_FRIEND diplomacy type. Right now it is pathetically meaningless. In particular, increase the priorities of the good proposals such as GIVE_GOLD, etc.

All the above changes are in diplomacy.txt. Make sure that you don't change the order of the various ProposalElements, else the game may crash in a few turns. Also, don't use the function
ChangeGlobalRegard(player, delta, explanationID).
I crashed the game a few turns after this was used.

Heck, some of these civs that loved me even began offering me gold! Also, at least one civ was at war with another, so there is some fight going on.

BTW, I also added an extra bit of diplomacy SLIC, to the effect that
"If the minimum distance between AI1 cities and AI2 cities is greater than 20 (or whatever you want), ConsiderDiplomaticState(...,MAKE_FRIEND,...)".
This may also have created the above lovebug. I was unable to verify if this piece of code is the one responsible for all that love, because I don't know how to access the player's current diplomatic states.

Clearly, other conditions can be similarly created, depending on the opponent's strengths.

Programming the AIs to hate the human is fairly easy - just add the check that ~IsHuman(player[1]) or some such in the code that spreads the love.

diplomacy2.slc (include this in script.slc):

int_t messarmysize;

HandleEvent(NextDiplomaticState) 'Distance_NextDiplomaticState_F' pre {

int_t mnctyapart;
int_t clsecity;
int_t dist_measure;

mnctyapart = 300;
clsecity = 100;

int_t i;
int_t j;
int_t play0;
int_t play1;
int_t db_index;
int_t ss_priority;

city_t capcity0;
city_t capcity1;
int_t flagthreat;

flagthreat = 0;

// capcity0 = player[0].capital; // Broken !!
// if (CityIsValid(capcity0)) {
// }
// else {
// capcity0 = player[0].largestcity; //Broken!!
// }

for (i=0; i for (j=0; j GetCityByIndex(player[0], i , capcity0);
GetCityByIndex(player[1], j , capcity1);

dist_measure = SquaredDistance(capcity0.location, capcity1.location);

if (dist_measure < mnctyapart){
if (dist_measure < clsecity) {
// hey, this guy is too close!
flagthreat = 2;
}
elseif (flagthreat == 0) {
// close, but not that close
flagthreat = 1;
}
}

}
}

if (flagthreat == 0) {
// Be nice to the guy! He's too far
ss_priority = 5000;
db_index = DiplomacyDB(DIPLOMACY_MAKE_FRIEND);
ConsiderDiplomaticState(player[0], player[1], ss_priority,db_index);

}
elseif (flagthreat == 2) {
// this guy is real close. he'll be a pain!
if (player[0].militaryunits > 2*player[1].militaryunits) {
//Go get him!! he's very weak!
ss_priority = 5000;
db_index = DiplomacyDB(DIPLOMACY_PROVOKE_WAR);
ConsiderDiplomaticState(player[0], player[1], ss_priority,db_index);
}
elseif (player[1].militaryunits > 2*player[0].militaryunits) {
//Don't provoke!! he's very strong!
ss_priority = 10000;
db_index = DiplomacyDB(DIPLOMACY_DEFAULT);
ConsiderDiplomaticState(player[0], player[1], ss_priority,db_index);
}
}

I also changed diplomacy.txt (that's the file that defines the different diplomatic states). The most important change I made there is setting the

invasion,incursion regards in DIPLOMATIC_DEFAULT equal to 0 per turn.

Right now, the way it is set, the AIs soon start hating each other because a couple of solitary enemy units are wandering about their empire.

In the most recent game I played, I have the AI warring with at most one or two other AIs; a big change from my earlier games where everyone hated everyone else!