This is correct. Morale will go down without the win bonus and will definitely affect your game to some degree. I dont know how the win bonus affects your morale in terms of actual numbers yet, I did not do that test, but I know that I was losing more games than I ever have before without ANY win bonus.
BTW, the test I did was with morale at 25% or one click of win bonus. The thread is around here somewhere...too lazy to look it up sorry.
I used to have it at 100% and took the hit in the $$$ as it was nothing at levels 1-4, but I now have it at 50% on some lower accounts and only at 25% on my level 7 account since I need the money more than wins (Token buyer in my league = cant win league so dont bother with win bonus)
It comes down to do you need the extra chances at winning MORE than you need the $$$$$$$$$$.
With 4 games to go, dont worry about the money since you get a nice package at the end/start of the season. click on the FB movies for extra cash. I have received a ton of $$$ over the past week and get ~$2M/day at level 7. For some reason I cannot get the booster vids, but at level 7 right now, I need the $$$ more.