You can have for a while a group based on opposition of things that everybody agrees on. But even in such case, unless there is some shared vision on how to achieve that, there is soon infighting and thus an unhealthy culture develops.

Downvoting for disagreement or if you don’t understand somebody does not contribute to a healthy culture here.

I'm taking what you wrote at face value. You wrote that healthy culture "does not come from opposition of something", but in reality, one can't have a healthy culture without opposition (in words and in deeds) to bad things.

I obviously want my social media to be opposed to human traficking. However, if that is literally its only defining characteristic, it doesn't sound like a fun place to hang out.

Although I'd go further and add "only" before "defining yourself", I think there's wisdom in that statement. Some political parties have fallen into that trap, reactively opposing anything "the enemy" is for even at the cost of their constituents' health and happiness.