It's not subjective at all, it's a judgement of whether speech aligns with cooperation or attack as understood in human nature within tribes/communities. Pro-s

It's not subjective at all, it's a judgement of whether speech aligns with cooperation or attack as understood in human nature within tribes/communities. Pro-social doesn't mean "positive" or "good" or "correct", it means that it's an attempt at progress or improvement for the community, from some sincere point of view. "We should kill all nazis" is pro-social in terms of sincere critique, and anti-social in the threat of wanting to kill them. If we're at war with nazis then calling to kill them is likely mostly pro-social. If they're part of our tribe, whereby you are threatening your own people, then it's definitively anti-social. "We shouldn't accept nazis" is fully pro-social, and so is "we should all be nazis". We can instinctively tell when someone is trying to be cooperative or offensive (attacking, deliberately destructive) to us in some way. We have the capability of recognizing it even if there are cultural/moral/logical (epistemic) divides. We just have to take the time to understand the other party's perspective and situation, then we can categorize their behavior.