1) "...[E]thical to me IFF you don't make stuff up." I think you can have propaganda that uses only facts, but in a disingenuous manner. You just don't mention _all_ the facts, and/or put a lens on the wrong perspective. Is that "dishonest?" I'm not sure - maybe a misinterpretation?.
As an example, you can see this all the time with the arguments against global warming: "some studies show that temperatures are not increasing." If you look hard enough, you'll find data points and/or papers that argue against global warming, but they're a very very minor # of studies, that it's not a fair perspective or lens on the arguement.
2) "I find it imperative to do so." I am not a Facebook fan-person by any means, but I'm not sure I find it morally _imperative_ that folks rally against what they are doing. I have a hard time believing that the 1000's of employees that work there are all evil people, but rather the majority are probably well-intentioned and may just need a correction of direction. Can I prove this? No, but if they were, say, selling nukes to ISIS or something at that level, then I might agree with you a bit more.
Then again, you did say "propaganda" campaign, so I guess there was your assumption of dishonesty.