Under dailyFetish(person) in Expansion.gd, remove the lines:
elif person.dailyevents.count([i]) + rand_range(0,2) < globals.fetishopinion.find(person.fetish[i])/3 && rand_range(0,1) <= .1:
if globals.fetishopinion.find(person.fetish[i]) >= 0:
person.fetish[i] = globals.fetishopinion[globals.fetishopinion.find(person.fetish[i])-1]
That will leave the chance of an automatic increase with no chance of automatic decrease. You could also play around with the rand_range to try to lower frequencies, but I haven't found an acceptable frequency that people liked yet so have it disabled but with a setting to reenable it in case people want to add that slight layer of difficulty back in.