A/B testing of link colors if fine, of course. Manipulating users' emotions -- not so much. Interfering in elections, without proper disclosure, and providing data of people who did not agree to it to support just one side -- yes, quite despicable. And if it weren't, then what's the problem with Cambridge? It shouldn't really matter that that one time they've supported the candidate that, I make a guess, you liked.
And it's not like the give you a new setting that you need to update. They remove, completely, the capability that you had. You just can't keep it "up to date" with the same discoverability settings you had before just because Zuck decided that you shouldn't.
Of course, it's not like every FB employee is given an operatic villain's costume during their orientation. But if you work there, you're enabling it.