so if I attacked one then the whole galaxy declared war on me
Wait a second, did you attack the Altarians?

As population increases, the effect of morale (whether as a racial bonus or as a structure) goes down. I've provided the relevant numbers below (which I initially posted elsewhere), although for your purposes only the first three columns are relevant.
I don't have a 9B number because I didn't play the Yor for this test.
Pop: malus, multiplier, morale to hit cap (100) after depreciation, morale to balance out pop malus after depreciation
8B: -18%, 0.82, 122, 22
10B: -25%, 0.75, 133, 33
11B: -28%, 0.72, 139, 39
12B: -32%, 0.68, 147, 47
13B: -36%, 0.64, 156, 56
14B: -40%, 0.60, 167, 67
15B: -44%, 0.56, 179, 79
16B: -48%, 0.52, 192, 92
17B: -52%, 0.48, 208, 108
18B: -57%, 0.43, 233, 133
19B: -61%, 0.39, 256, 156
20B: -66%, 0.34, 294, 194
21B: -70%, 0.30, 333, 233
22B: -75%, 0.25, 400, 300
23B: -80%, 0.20, 500, 400
24B: -85%, 0.15, 667, 557
25B: -90%, 0.10, 1000, 90
What this means is if I have a virtual reality center (+40% morale) on a planet with 13B population, I will get 40*0.64 or 25.6 points of approval out of it on that planet. After everything is accounted for, this is truncated, so I only get 25 out of one-but if I had two I'd get 25.6*2 or 51.2 which truncates to 51.