Presumably it's OK to voice one's opinions on social media, but:
1. Is it acceptable for private interests to do the same?
2. At what point does something turn from personal opinion to propaganda?
3. Is it more problematic that a private entity (e.g. a PR firm) is _pretending_ to express an honest opinion? Would this be acceptable if this were a group of up-front political activists instead?
Personally, I'd draw the line at private interests trying to influence public opinion. Sadly, this is a process as old as the hills. Marketing and propaganda have existed for a long time, it just seems like it's become much harder to pin it for what it is in the era of social media.