How we treat advertising on social media is a matter of convention, a social negotiation. If we agree that it's just targeting demographics and not endorsing the actual content, then that is what it means, and advertising dollars wouldn't care about the content. The effectiveness of social media advertising doesn't need to be sensitive to content.

And maybe it isn't totally different from newspapers and TV news programs. Just like we don't associate advertising on news media with the often violent and disturbing content of the news itself, we don't need to treat social media advertising as endorsing its user-generated content. And in fact, we haven't been doing that until the recent YouTube controversy.

You're a german company. You sell cars. A community of gun enthusiasts hosts your ad. You deny it on moral means.

This has nothing to do with cars. People who buy guns can, and often do, buy cars. No relation. Was your buy going to be wasted?